Ornithology Course

2009-12-10T07:30:00.000-08:00

Introduction
What is a Bird?
Ornithology (Ornithology and birding)
Flight (Advantanges and adaptations for flight)
Origin and Evolution of Birds (The evolution of flight)
Taxonomy and Systematics (Species and evolution)
Ethology (Behavior, innate vs. learning, personal behaviors)
Social Behavior (Communication, Territory, Flocking, Courtship and Breeding, Nesting, Incubating, and more)
Migration (The whys and hows of migration, What about birds that don't migrate?)
Feathers (Kinds, molt, color)
Ecology (Extinction, Geographical Ecology, Population Ecology)
History of Ornithology (Very brief, mostly American)
Concluding Remarks (You could well start here--feeding birds, binoculars, birding organizations)

Barred Owl

Introduction

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This ornithology course originated from lecture notes that I developed over the years. I have retired from teaching and see little reason to have this resouce, such as it is, gather dust in some drawer. In this blog format, I offer it to you as a free, non-credit, self-study exercise. As such, you many expect little or no interaction from me (although I will be glad to hear about possible editorial improvements).

This blog is not intended as an all-inclusive course. For example, I also taught courses in Ecology and Evolution, so many fundamental aspects of those courses are not found here. It would be wise, then, to have a General Biology textbook, in case something is not fully explained here. I expected students taking this course to purchase an ornithology textbook. Later, students bought Thayer's CD-ROM disk, Birds of North America, that has a brief textbook embedded within it. Either way, you can go into various subjects in more depth or check out areas that may be neglected here. Students should also make extensive use of Google or other search engines. Clicking on many words in this blog will lead directly to Google, whence students can retype the term and see where Google takes you. Just don't forget to return to the course!

During a "normal" Ornithology course, students would have an extensive laboratory experience. I emphasize heavily field identification. Students should buy any field guide and spend up to four hours per week trying to identify birds. Field work is the skill that many students will use throughout their lives and makes an Ornithology course especially valuable. (What is a "normal" Ornithology course? I suspect that each ornithologist would come up with a different course, depending upon the interest of the scientist! This situation is certainly the case with this course.)

I received my Ph.D. from Louisiana State University. While there I took Ornithology courses from Dr. George H. Lowery, Jr., and Dr. James Van Remsen. In many ways, this course evolved from those graduate courses. This course is dedicated to my wife, Erika, without whose assistance and support, I would not have enjoyed a successful ornithological career.

Common Loon

Ornithology

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Song Sparrow

What can ornithology do for you? Why study it? In no other branch of science have amateurs played such an important role: Margaret Nice's Life History of the Song Sparrow is a classic example. My students have written papers in their state bird journal. But I don't mean to make you all into scientists. Bird watching (birding) is a hobby for many and a passion for some. Housewives (and even househusbands) trapped at home get an outlet by keeping track of the varieties of birds at outdoor feeders. You'll never get bored traveling between cities to--you may even enjoy the trip. Trips across the country become down-right exciting as you search for and find new and different species. You become more in tune with the world, our ecosystem.

Goals and Supplies

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Birding's beauty is that it only takes a field guide and a pair of binoculars--WHICH IS ALL YOU NEED, AT LEAST 7x35, (but 8x or 10x are better; the second number is your field of vision, so a big number there is a good thing), walking shoes and old clothes. More on these subjects are covered in the concluding remarks section of this course. If you are interested, two exellent ornithology texts are Gill's Ornithology, published by Freeman and Welty's The Life of Birds. Current students have a rudimentary textbook embedded in their CD-ROM. Thayer's Birds of North America.

THE GOALS OF THIS COURSE ARE TWO FOLD:
1) to enhance your appreciation of birds.
2) to encourage you to make observations or investigations of your own.

My name is Dan Tallman. I am an ornithologist by training. I will try to keep unnecessary technical terms out of this course, which is often hard for someone who is completely immersed in his or her scientific field. But, hopefully, as a birder by hobby, I can also recognize for you which terms are important to include.

As a first assignment, study "topography of bird" and "parts of wing" in any text or field guide. How do bird arms and legs compare the human ones?

Birding

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Bald Eagle

During this course I expect you to keep a life list of the birds you see--either in the book or on a checklist. Of course, if you keep it up after the course is over is up to you. Many birders keep a life list of species seen throughout their whole lives. I keep track of the dates and places all around the world. (Some people are into cathedrals and Rembrandt's but I race out to the nearest swamp!) If you keep up birding seriously, you might want to start a Year List in addition to a life list, monthly lists state lists, big days, world lists, semesters, country lists, Christmas counts, spring counts are all examples of lists people keep. Birding can quickly become a sport that can involve any number of players. The South Dakota Ornithologists' Union saw 150 species in one weekend in Sisseton, South Dakota. The sport can be costly too--once friends saw a Bald Eagle and jumped out of their jeep. Unfortunately, nobody turned the jeep off, so it proceeded into a lake! A fellow named Vardemann wanted to list 700 species in one year in North America: he fell 2 short and spent $30,000 trying! (All sports have their fanatics.)

Some will spare no expense to see a new bird: a Ross's Gull in New England brought out thousands from all over the country to some poor sucker's front yard. A Brambling in Bismark, North Dakota, was kept quiet for fear of intruding birders. Black Rails have been literally trampled to death by the hordes of bird watchers searching for them! But, by in large, folks are mostly sympathetic to birders--many don't hunt and so aren't destructive to private property (although a farmer was once upset at my walking across his newly planted turf). In fact, birdwatchers have somewhat of a bad name among hunters as some are vehemently anti-hunting. But, to be a good hunter, you must be a good bird identifier. I have always believed that all hunters should have to have a bird identification license. If you can't tell a grebe from a duck, you should not have a shotgun in your hand--so to become a good hunter is another reason to take ornithology

If you don't become a rabid birder that's OK too. Bird behavior is a fascinating study and you can specialize in just the birds of your farm or backyard. Any educated person ought to know the parts of the Thanksgiving turkey he or she is carving up. I firmly believe that people should know the plants and animals of their home state--in the past, this knowledge has always been the mark of an educated person.

Birds have always had a great aesthetic value to people--perhaps because of their ability to fly: (even though this ability has left birds remarkably stupid: having a bird brain means you don't have to think about problems, you just fly away).

Welty included this quote in his ornithology textbook: "When the anthropologist Hortense Powdermaker surveyed native school children of Northern Rhodesia and asked them, given a free choice, what they most wanted to be, nearly half the boys wanted to be birds. Almost half the girls wanted to be boys, but about one quarter of the girls wished that they, too, might become birds."

Birds, of course, have great value for people: not only because of all the insects and weed seeds they consume (without birds, of course, we would have ecological catastrophe) but because they act as an index to our ecological well being--just as old-time miners took canaries into mines to warn of deadly gas concentrations.

This is not to suggest that birds can not cause damage to farmers. One of the favorite quotes of the ornithologist Alan Phillips was "If ever I am accused of destroying the crops, I would certainly want an ornithologist to defend me." A farmer, however, should be able to tell which birds are actually doing the damage or he may actually be costing himself money in the long run.

What is a Bird?

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Write down an answer and see how it compares to my 6 attributes birds. Most birds fly, but flight is not exclusive. Can you list the 4 groups of animals that are capable of TRUE FLIGHT? (Hint: gliders don't count.) See answer at the end of this post. Bats also fly but birds are far more modified for flight than bats. Indeed, because of flight and the modifications to it (the aerodynamic demands of flight), birds are remarkably similar. There is far less difference between an albatross and a hummingbird than an elephant and a shrew or monkey.

TO RECAPITULATE:

A bird is a flying vertebrate with feathers. (Cursorial birds (= ratites) are believed to have evolved from flying ancestor.)

Black-footed Albatross

Black-chinned Hummingbird

Answer to question above--This is kind of a trick question, since one group is extinct.
1. Birds 2. Bats 3. Insects 4. Pterosaurs

What is a Bird? 2

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A bird is in the animal Kingdom. It is a in the phylum Chordata, subphylum Vertebrata (fish, amphibians, reptiles, and mammals are other examples of vertebrates). As such, birds have a backbone, notochord, and pharyngeal clefts. (Be sure you can define these terms.)

They lay eggs with shells (other egg-layers include reptiles and some mammals (which?)).

They have a 4-chambered heart (as do some reptiles and all mammals).

Birds are warm-blooded (as are mammals).

And birds EXCLUSIVELY have feathers, outgrowths of skin that cover and streamline the body

Great Blue Heron

What makes birds special is their ability to fly

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Tundra Swan

Some of the advantages of flight:

1) Long distance movements (migration). Resident animals are limited by lower critical seasons. Migrants capitalize on seasonal abundances.

2) Short distance movements local access to food improved. Fruit, flowers, seeds are all patchily distributed, yet 27% of all birds are specialized to eat just these items. In fact, the flowering plants evolved at the same time as did birds, suggesting co-evolution.

3) New feeding modes opened. Flying insects now available (10% of birds specialize in eating flying insects). Flight also offers birds quick access to trees.

4) Escape from predators--(perhaps less important since flying predatory birds appear early on-geologically)

Adaptations for Flight 1

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Most bird adaptations are geared toward adaptations to flight: economy of weight, increased power, aerodynamic soundness.

To this last concern: a bird's mass is centered at wings and legs (= center of power), the size of limbs, head, and tail are reduced, and body weight is suspended under backbone to enhance stability.

Brown Thrasher. Note the nictitating membrane covering the eye.

Adaptations for Flight 2

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1) skeletal

a) bones are hollow with internal braces for support the skull is particularly light.
b) no teeth
c) no bones in tail
d) reduction of bones and general fusion of bones
e) Study and draw a picture of the bones and feathers of the wings.

When studying wings, note especially: humerus, ulna, radius, 2 carpels, carpometacarpus with 3 digits. How does this compare with a human arm? Note also the locations of the following structures: primaries, secondaries, allular quills, under wing coverts, axillars, scapulars, lesser, median, and greater secondary coverts, greater primary coverts.

f) Study and draw a picture of the bones of the legs

When studying the legs, note: femur, patella, fibula, tibia, tarsometatarsus, hallux (= toe 1), phallanges 2-3-4 (2 being inside). How does the leg of a bird compare to a human leg?

g) other fusion and modification of bones include: 1) pelvic and pectoral girdles are fused (the pelvic is now called the synsacrum); 2) the keel and sternum are modified for pectoral muscle attachment; 3) coracoids present to prevent flight muscles from squashing the body and lungs. Ribs are strengthened by means of uncinate processes.

Adaptations for Flight 3

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Nervous modifications

The cerebellum is enlarged (the area of the brain responsible for coordination and balance). In birds, the cerebellum is relatively bigger than in any other animal.

Birds' eyes are very large. Proportionally, the eyes are 10-15% larger than people. Some hawks have eyes our size but they have much smaller bodies. Sometimes eyes touch inside the head. The retinas are 1-1.5 % thicker than mammals'. The rods and cones are more abundant in fovea (where cones are concentrated) = million cones/sq. mm (200,000 in people). A hawk's vision is 8x better than a person's. Bird eyes have oil droplets that increase contrast and reduce haze. Hawks and other fast flyers often have 2 fovea: central for side vision, temporal for front vision. Most sensory cells are in upper part of eye.

Bird eyes have 2 peculiar features: 1) pectin, a folded vascular structure projecting from optic nerve. The exact funtion is unclear: nutrition and shading? 2) sclerotic ring, ring of bones around edge of eye. The ring fixes it so eye can't move: makes for telescope-like eye! Bird compensates for lack of movement by having really flexible neck.

Swainson's Hawk

Adaptations for Flight 4

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Olfaction and Hearing

Most birds have a poorly developed sense of smell don't taste much either, mostly swallow food whole, probably as a weight economy. Kiwi has the best sense of smell. Recent studies have shown than petrels smell their prey out in the ocean. ROBINS EYE WORMS, they don't listen or smell for them.

Turkey Vultures smell well and locate carrion that way. Pipe companies have added carrion smell and looked for vultures to find leaks but sight may be more important---in the jungle of Ecuador, I met beetle collectors who buried cans of excrement to catch their insects. Vultures could not see or smell the shit, but quickly gathered around, perhaps cued in by the flies around the cans.

4) EARS. Birds have some of the best hearing of animals, even though they lack pinna (= streamlining). Barn Owls can catch in total darkness. At least two birds use echo-location like bats: Oilbird and Cave Swiftlet. (From the swiftlet comes birds' nest soup: the nests are made of sticks and dried bird saliva.)

Turkey Vulture

Adaptations for Flight 5

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Muscles. Pectoral muscles = 15-40 % of bird's weight (vs. 1-2 % in people). Another difference is that the muscle that pulls the wing back (= supercoracoidius) is attached to the sternum rather than the backbone (= better balance for flying). There are no heavy jaw and facial muscles and no heavy back muscles.

EXCRETORY SYSTEM. There is no urinary bladder.

DIGESTIVE SYSTEM. Birds eat high energy foods--there are almost no strictly vegetarian birds. They have efficient digestive enzymes.

Cedar Waxwing

Adaptations for Flight 6

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Masked Booby

Respiratory and Reproductive Systems.

Birds' respiratiory systems contain air sacs which are outpockets of the trachea and lungs (a bird can breath through a broken elbow). See a textbook explanation. They comprise, along with lungs, 20% of a bird's body volume. The airsacs allow for a one-way air flow in the lungs, which results in there being no dead space.

1) airsacs cool the bird's high metabolism
2) increase buoyancy
3) cushion gannet-like dives

REPRODUCTIVE SYSTEM

1) There is a seasonal regression of gonads (1/1000 reduction in testes size)
2) No live young....rapid egg production
3) One ovary (liver moves centrally for balance); a curious exception may be in hawks, which have two ovaries.

So there you have some bird adaptations for flight. Left off is a great deal of avian physiology, a subject I hope to return to now and again

Origin and Evolution of Birds

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What was our definition of a bird?

Many modern vertebrate zoologists would change that to: "reptiles with feathers." Indeed, one researcher claims that birds are all that is left over from the dinosaurs--he holds for various reasons that many dinosaurs were warm-blooded. It could be that we don't have bird feeders but dinosaur feeders in our backyards. There should be a lot of material on the Internet on birds and dinosaurs. Try Googling the debate.

In any case, reptiles and birds (esp. crocodiles and birds) share a great number of features--so many that there can be little doubt but that they are closely related to the point that they once shared common ancestors. This common ancestor is thought to be THECODONT dinosaurs back in the TRIASSIC period of the geologic time scale 225 million years ago. (I once asked for the geologic time scale for extra credit-another mark of an educated person.)

1) skeletons similar: joints between skull and jaw the same in crocs and birds; ankle joints also similar
2) both have scales on epidermis & lack skin glands
3) brain structure is similar
4) blood proteins and red blood cell's are similar
5) embryological development is similar
6) hard-shelled eggs
7) fossil record

There are 2 theories about the evolution of flight (and whether Archaeopteryx, the first bird we know of, could fly). Traditionally, Archaeoperyx was thought to be arboreal and agile --a jumper and a glider that couldn't fly, just an arboreal gliding 2-legged dinosaur. John Ostrum (Yale) decided Archaeopteryx was not arboreal but cursorial. The skeleton does not indicate a climber or a glider but a bipedal animal that captured prey with forelimbs. Feathers evolved for heat conservation (like fur): Jurassic temperatures were cooling. SO WHY WERE THERE WING FEATHERS? By flapping proto-wings, the birds could generate lift for higher and higher jumps after prey.Whatever the case, birds are poorly represented in the fossil record and there are few avian paleontologists.

9000 species are alive today, in 30 orders, and 150 families. In addition, there are extinct fossils.You should be familar with the scientific names of the orders of the birds you see.

The class Aves peaked in the Pleistocene (about a million years ago). Madagascar had elephant birds = 1000 lbs and 2 gallon eggs. South American had 6' tall birds with foot-long bills that ate deer and pigs. California had vultures with 17' wing spans. New Zealand had Moas 12 feet tall.

Flight is the #1 reason birds are successful. Another reason birds are successful is thermal regulation. They are able to control enzyme reactions for maximum rate. This gave them a competitive advantage, especially when it got really cold at the end of the Mesozoic era

Archaeopteryx: the first bird

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Archaeopteryx means "beginning wing." The fossil was found in Barvaria in 1860. It was always thought to be rather much a "missing link" between birds & reptiles. It comes from Jurassic period 140 million years ago and was a pigeon-sized bird. Certainly this was not the first bird, just the first we know of. Recently fossils of equal or greater age have been discovered in China.

Archaeopteryx had feathers identical to modern ones but otherwise was more a reptile than a bird:
1) teeth
2) vertebrae in tail
3) reptile-like skull
4) trunk skeleton like reptile (i.e., did not have fused clavicles)
5) clawed fingers
6) pelvis of three separate bones.

Flightless Birds

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Flightless Galapagos Cormorant

The few flightless birds (called Ratites) of the world are probably local adaptations to peculiar habitats and they themselves probably evolved from flighted ancestors. They have the same bones in their wings and bodies as do birds that fly. Intermediates between flying birds and ratites are known. Ratites are mostly known from islands--why? Penguins are flightless birds who "fly" through the water. Interestingly, the major ratites (ostriches, emus, and rheas) share the same ectoparasites. Does this mean they rubbed shoulders back before continental drift?

Taxonomy and Systematics

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Taxonomy = naming (nomenclature) and classifying.
Systematics = evolutionary relationships.

Although I've said birds are remarkably similar, there is an astonishing range in size. A Bee Hummingbird has a wing span 4 in and weighs 0.5 oz. A Wandering Albatross' wing span is 11.5 ft and it weighs 25 lb. Ostrich weigh 350 lb.

Bird shapes (i.e., bills, wings, and feet) reflect adaptations of birds to habitat and feeding methods. By looking at bird parts, you ought to be able to predict a bit about how they feed and behave. This is called predictive morphology

We name birds according to a system of binomial nomenclature.

Ruby-throated Hummingbird

Linnaeus

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In 1758, Linnaeus wrote his Systema Naturae, in which he attempted to name all the species of the world in two names: Genus species

This is part of a larger zoological hierarchy: Kingdom, Phylum, Class, Order, Family, Genus, and species. You can recognize family names because the end in idae; you can recognize orders because they end in iformes.

A Kingdom is defined as a group of phyla that are more similar to each other than they are to any other group of phyla. A Phylum is defined as a group of Classes that are more similar to each other than they are to any other group of classes. And so forth....

Only the species is objectively defined: the only real object.

Western Grebe with young

Species

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A species is a population whose members are capable, at least potentially, of freely interbreeding and producing fertile offspring. A species is composed of a group or groups of interbreeding populations that are reproductively isolated from other such groups = AN INTERCOMMUNICATING GENE POOL. In practice, however, you seldom get a look at gene pools. This has led to two species concepts.

Northern Cardinal

Biological vs. Morphological Species Concept

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On paper The Biological Species Concept looks great: if two populations of birds can interbreed, they must be the same species. But it is difficult to apply.
We tend to look at morphology rather than GENE FLOW.

HOW DIFFERENT DO TWO POPULATIONS HAVE TO BE TO QUALIFY AS DISTINCT SPECIES?

MORPHOLOGICAL SPECIES CONCEPT

In birds, enough is known to follow, generally, the biological species concept. We do have problems when two populations show limited hybridization. How much is allowed before they are proclaimed to be two well marked RACES of the same species?

Rose Breasted Grosbeak and Black-headed Grosbeak

These two birds interbreed, but are they the same species?

DNA

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With the advent of DNA technology, we can begin to actually see gene pools. Recombinant DNA is revolutionizing bird taxonomy. Basically, strands of DNA are split and hybridized (recombined with DNA from a different species). The more similar two strands of DNA are, the more stable the hybrid DNA will be. The results are sometimes surprising. Loons and Penguins are more closely related that previously thought. Flamingos are closely related to geese rather than herons. Sandpipers are close to doves. New World Vultures are close to storks. Warbling Vireos in the Black Hills of South Dakota are probably not the same species as those in the eastern part of the state.

DNA systematics are not without critics. Evolution is assumed to proceed at the same rate in all groups of birds. Similar sequences of DNA bases are assumed to be the result of common descent rather than accident. Never-the-less, as more and more DNA evidence is accumulated, the systematics of North American birds will be in a state of upheaval for the next few years.

Warbling Vireo

Races

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Wide ranging species often range over different environmental conditions and adapt to them, creating differences in morphologies. If they are significantly different (i.e., if you can tell where a populations of animals came from), they are considered to be a race or subspecies. Subspecies are separated only geographically, not reproductively. They are given taxonomic stature in a trinomial, for example:
Turdus migratorius migratorius is the race of robin found across most of eastern North America, including eastern South Dakota. T. m. propinquus, on the other hand, is sightly smaller without white tail spots and found in Western US.

Mostly differences are too small to be treated by anyone but professional taxonomists, but, problems do arise to upset even the most casual birdwatcher, prompting even letters to the editors, like when the Baltimore and Bullock's Orioles were lumped together as the Northern Oriole. (Note, however, that recent evidence suggests that there is only very limited hybridization between these populations, and in 1996, the two were resplit.)

Why is there more than one species of bird?

American Robin

Speciation

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Speciation is almost always allopatric and not sympatric. That means, for two populations to speciate, they need to be isolated. Once isolated, genetic differences accumulate. This is called evolution. Evolution means that the most fit leave the most offspring. In other words, the most fit leave the most genes. Thus, over time. the genes that constitute being the most fit become prevalent in a population. Evolution is inevitable. Given enough time, speciation probably occurs in all isolated populations. The question is, do they breed if they come back in contact (a zone of secondary contact)? If reproductive isolating mechanisms have appeared, then speciation has occurred. A classic example of this is Darwin's Finches on the Galapagos.

There are many ways in which populations can become fragmented. These ways include isolation on islands, mountain tops, and glacial refugia. Once fragmented, the populations develop isolating mechanisms, which keep them from interbreeding in a future zone of secondary contact.

Lazuli and Indigo Buntings hybridize where their ranges meet in the midwest.

Galapagos Finches

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The Galapagos Islands were apparently colonized by at least a male and a female finch from the mainland of South America. There are now 13 closely related species of finch on the islands. (Perhaps not coincidentally, there are about 13 major islands in the archipelago.) The thought is that these birds built up numbers on the first island and then spread out to the others, only to become reproductively isolated on them. When isolated, they built up barriors to reproduction with the birds they left behind. So, from one species, there evolved 13. Because they have been isolated for a relatively short time, they look pretty much the same except for bill size. Events like this of multiple speciation are called adaptive radiation.

A similar adaptive radiation is thought to have happened with the Hawiian Honeycreepers in the family Drepanidae. Because these islands were colonized long before the Galapagos were, the various honeycreepers show a whole lot more diversity than do the Galapagos Finches.

Large-billed Ground Finch

Medium and Small-billed Ground Finches

Isolating Mechanisms

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Yellow-bellied Sapsucker

A number of things can happen in zones of secondary contact:

1) No interbreeding at all (or almost none). Eastern Meadowlark and Western Meadowlark are examples.
2) Low level hybridization (5-10 %) in low populations. It my be better to make it with anyone rather than nobody at all. Secondary areas of contact are usually at edge of optimum range for both species and birds don't live more than 1 or 2 years normally. Examples include Indigo Bunting and Lazuli Bunting and Golden-winged Warbler and Blue-winged Warbler.
3) A complete breakdown of isolating mechanisms with almost no pure birds in zone of secondary contact. For example, Audubon's Warbler and Myrtle Warbler are now called Yellow-rumped Warbler.
4) Same as 3 but with extensive genetic introgression into each population. For example, Yellow-shafted Flicker and Red-shafted Flicker (Northern Flicker): orange feather shafts are found well out of the expected ranges.

Hybrid Indexes are often constructed to study just what the situation is. In the early 1950's, Baltimore Oriole and Bullock's Oriole hybridized extensively in a study area in the Great Plains. You could draw a graph that showed pure Baltimore plumages on the left and pure Bullock's on the right. Most birds were a mixture of plumages, with the majority being about half and half. In 1973 a fellow went back to these localities and found selection against hybrids, most birds were pure. Apparently zones of secondary contact in the midwest are not stable. Check your field guide and see how these species are treated. Old books treat them as different species, books written in the 1980's consider them to be the same, and the most recent books treat them as different species.

Apparently people have caused many previously allopatric species to become sympatric--we have forested the Great Plains and created a broad front of contact. Birds that have come together include flickers, grosbeaks, and buntings.

By the way, sympatric speciation is possible. How might that happen? The little evidence we have for sympatric speciation in birds involves hybridization wherein the hybrids breed true rather than back to parental types.

Zones of Secondary Contact

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A number of things happen in zones of secondary contact:

1) No interbreeding at all (or almost none). Eastern Meadowlark and Western Meadowlark are examples.
2) Low level hybridization (5-10 %) in low populations. It my be better to make it with anyone rather than nobody at all. Secondary areas of contact are usually at edge of optimum range for both species and birds don't live more than 1 or 2 years normally. Examples include Indigo Bunting and Lazuli Bunting and Golden-winged Warbler and Blue-winged Warbler.
3) A complete breakdown of isolating mechanisms with almost no pure birds in zone of secondary contact. For example, Audubon's Warbler and Myrtle Warbler are now called Yellow-rumped Warbler.
4) Same as 3 but with extensive genetic introgression into each population. For example, Yellow-shafted Flicker and Red-shafted Flicker (Northern Flicker): orange feather shafts are found well out of the expected ranges.

Hybrid Indexes are often constructed to study just what the situation is. In the early 1950's, Baltimore Oriole and Bullock's Oriole hybridized extensively in a study area in the Great Plains. You could draw a graph that showed pure Baltimore plumages on the left and pure Bullock's on the right. Most birds were a mixture of plumages, with the majority being about half and half. In 1973 a fellow went back to these localities and found selection against hybrids, most birds were pure. Apparently zones of secondary contact in the midwest are not stable. Check your field guide and see how these species are treated. Old books treat them as different species, books written in the 1980's consider them to be the same, and the most recent books treat them as different species.

Apparently people have caused many previously allopatric species to become sympatric--we have forested the Great Plains and created a broad front of contact. Birds that have come together include flickers, grosbeaks, and buntings.

By the way, sympatric speciation is possible. How might that happen? The little evidence we have for sympatric speciation in birds involves hybridization wherein the hybrids breed true rather than back to parental types.

At various times, Baltimore Orioles (above)

and Bullock's Orioles have been considered to be the same species

How does all this naming and systematics help you?

2009-12-08T11:05:00.000-08:00

Look at the table to contents in your bird guide: the birds are presented in a nonrandom order, from the birds thought to be most primitive to those that have the greatest cluster of advanced characteristics. This order is not sacrosanct! But it does tell you the latest scientific thinking on the order in which the groups descending through time. Knowing this order will help you quickly find groups of birds that you are trying to identify.

I am not asking you to memorize scientific names (besides orders) but, as you look at the various pages in the book, say warblers, by knowing that the Black-and-white Warbler is in the genus Mniotilta--you know its significantly different from Dendroica warblers. Vermivora warblers are different yet. With practice, these genera can be recognized in the field.

Unlike other animal groups, because the AOU checklist has been so religiously followed, common names really can be used for North American Birds and, indeed, may sometimes be more stable.

Black and White Warbler

Blue-winged Warbler (Vermivora)

Chestnut-sided Warbler (Dendroica)

Bird Behavior

2009-12-08T11:00:00.000-08:00

The study of behavior (ethology) is where biology and psychology merge. Ethology has a whole body of terminology that we will only skirt here. Most of ethology has been built on ornithological studies of ethological pioneers: Konard Lorenz and Niko Tinbergen.

Basically they have looked for the answers to two questions:

1) All behaviors must have functional and biological significance. Behavior should incur evolutionary advantage to the individual, otherwise it will be selected out. Even behavior that seems trivial may be evolutionarily important. Black-headed Gulls always carry away empty egg shells. When ethologists put shells near the nests, crows found them and ate their young. Many behaviors are important for species recognition--and are also quite complex--IT IS IMPORTANT THAT THE BEHAVIORS ARE PERFORMED CORRECTLY. This leads to stereotyped or ritualized behavior which is often species specific. Ruddy Ducks bobbing their heads almost seem out of control--and, indeed, they may be.

2) Is behavior instinctive or learned ? Many ethologists now believe that there is a continuum between the two--many behavior patterns are subtle combinations of the two (an example may be the learning of bird song. Apparently birds have a rough template of bird song in their brain, but they need to smooth it out by learning.) On one side, you have species-specific actions like head scratching. All house sparrows scratch above their wings (indirect scratching) while all crows scratch under their wing (direct scratching). These are innate behaviors.

Yellow-headed Blackbird

Innate Behaviors

2009-12-08T10:55:00.000-08:00

Western Gull

They are inherited. Ethologists call them FIXED ACTION PATTERNS (FAP's). What are some other examples? (hunting, courting?)

Most FAP's are blocked and seem to need an IRM (= INNATE RELEASING MECHANISM) to set them off. IRM's, in turn, require an outside RELEASER for each specific behavior pattern. In a famous example: When Herring Gulls feed their chicks, the chick pecks at the parent's bill. The parent, stimulated by this pecking, regurgitates a mass of food. So an ethologist offered Herring Gull chicks all sorts of parent head models. Regardless of shape of the head, the chick always pecked at those bills with red on them. Apparently the red on the parent's bill releases the IRM for pecking for the young, which, in turn, released, quite literally, regurgitating in the adult.

Of course many other behaviors are releasers: a female turkey will kill her own chicks if she can't hear them. European Robins have red breasts--orange in immature--males will attack red color in general, despite shape of the head (like a red mail truck). A flicker's mustache is probably a good example of a releaser. Many gulls with black-heades don't face each other since the sight of a black head releases aggression.

You can also have SUPER RELEASERS: European Oystercatchers prefer huge artificial eggs to their own!

--before moving onto learning, I should mention two or three other interesting types of behavior--

Personal Behavior

2009-12-08T10:50:00.000-08:00

Blue-winged Teal

1. Preening, arrangement, cleaning & general care of feathers. These are done with the bill, usually one feather at a time. Preening movements are usually stereotyped.
2. Head-scratching. This has been mentioned--some species are variable.
3. Bathing. Most bathe in water--House Sparrows bathe in dust. Wet birds can't fly efficiently so bird baths should be raised out of cats' reach.
4. Oiling after a bird is dry. They touch UROPYGIAL GLAND at base of tails. This waterproofs plumage and keeps feathers flexible, less likely to shatter.
5. Sunning. Birds often stretch out and ruffle feathers in sun. The exact function unknown--temp regulation? But done on cool days too!
6. Anting is another mystery. Some woodpeckers and many songbirds (Passeriformes) either passively let ants run or crush them into feathers. WHY? Secretions may discourage ectoparasites.
7. Comfort movements. These are stereotyped movements--fluffs, shakes, folds back feathers = feather settling; stretching; yawning; resting (with bill under scapulars).
8. Sleeping. Varies with and within species, some like resting but pigeons sleep with heads drawn in and bill forward.

Try Googling some of these terms (especially anting).

Other types of behavior

2009-12-08T10:42:00.000-08:00

Sometimes a behavior seems to occur out of context. Turkeys will often drink right in the middle of a fight or chickens will peck at nonexistent food before a fight. These are called DISPLACEMENT ACTIVITIES. They usually appear in conflict situations. Can you think of any examples from people? How about head scratching at a problem? Does head scratching really help solve your problems?

REDIRECTED ACTIVITY. Again, usually the result of conflict situations. The bird is afraid to attack intruder so it attacks its mate. Sound familiar?!

INTENTION MOVEMENTS. The bird starts an act but does not complete it--flicks wing, opens gape, snaps bill. All three of these behaviors are often ritualized and incorporated into more elaborate behaviors. For example, mating Herring Gulls preen themselves and/or pull at grass and both behaviors are often seen in aggressive situations too.

Red-necked Grebe with young on back.

Types of Learning

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1. HABITUATION. This is the simplest type of learning-- learning not to respond to a stimulus that carries no reward or punishment. At first young turkeys crouch in response to anything moving overhead--older ones crouch at anything unfamiliar but pay no attention to things like falling leaves.

2. CONDITIONING. Learning to respond to stimuli that initially means nothing--like Pavlov's dogs who salavated when a bell was rung since it was rung every other time they were fed. We know little about conditioning in wild birds, but birds learn to associate feeders with food.

3. TRIAL AND ERROR. Young insectivorous birds will often peck at most anything but get better and better at finding insects and then learn to avoid noxious ones.

4. INSIGHT (INTELLIGENCE). An animal solves a problem without trial & error. Common Ravens can distinguish up to number six. This is about the same as people who are shown a number of objects without time to count.

5. IMPRINTING. Imprinting happens quickly and carries no immediate reward. Baby mallards will follow a person only between 13-16 hr.; it's impossible before 12 and after 24. (Try Googling Konrad Lorenz and geese.). Birds imprint on sexual partners; song, selection of habitat (?), home territory (?).
Returning to the subject of behavior, in general, there are two types of behavior, personal and social.

Phainopepla

Social Behavior

2009-12-08T09:40:00.000-08:00

Most bird behavior involves more than one individual. These are the topics that I will cover:

Communication
Territory
flocking (feeding)
Courtship and mating (including nesting)

I won't talk about defense: i.e., fighting, threatening, or freezing. These can be read about on your own, either in your textbook or in an ecology text.

Visual Communication

2009-12-08T09:36:00.000-08:00

Blue Jay

Communication occurs when the activities of one animal influence the activities of another. Communication is primarily: VISUAL or VOCAL, although combinations certainly occur. Many are very stereotyped (DISPLAYS); i.e., gaping in American Goldfinch.

Visual Communication

1. THREAT DISPLAYS occur in hostile encounters and indicate the potential aggressiveness of displayer. Different species have different displays.
gulls: head up, open wings, bill downward.
many songbirds: head forward, horizontal with body, gaping with wings raised.

2. SUBMISSIVE (appeasement) display
Black hood of Franklin's Gull = threat display--but pairs must avoid aggression: during the submissive, FACING AWAY DISPLAY, birds turn heads away from each other. This way they can approach during courtship.

In general, submissive postures reduce the aggression of the opponent, indicates fear. Postures in a Blue Jay's crest angle indicates fear--the higher the crest, the more aggressive.
Hermit Thrushes are the only thrush to show Tail Raising: birds lift tail quickly. This serves both as species recognition and aggressive display: the higher the tail raise greater the aggressiveness.

3. BEGGING DISPLAYS: usually in young birds demanding food crouch, flutter wings, open mouths.

4. SEXUAL DISPLAYS Bring the sexes together and promote successful reproduction

American Goldfinch

Sexual Displays

2009-12-08T09:34:00.000-08:00

a) COURTSHIP male chases female

1) SOLITARY by male alone
2) MUTUAL by both sexes
3) COLLECTIVE by 2 or more males together

b) PAIR BONDING or PAIR-MAINTAINING DISPLAYS

1) sexual pursuit: male chases female and indicates readiness to copulate
2) courtship feeding: female gives begging displays, apparently to lower male aggression

c) FERTILIZATION DISPLAYS displays directly associated with copulation, often difficult to tell from courtship and pair bonding displays.

Royal Flycatcher

Evolution of Displays

2009-12-08T09:30:00.000-08:00

This is the work of Lorenz and Tinbergen. There is little evidence that most visual displays in birds are learned--they appear the first time the need arises. Furthermore, closely related species have similar displays that may have evolved from common and ordinary movements:

DUCK HEAD-TURNING DISPLAY. Some male ducks touch part of a wing with bill some touch speculum ( = display flag). Others nervously preen wing feathers ( = derived from displacement activity). Thus it seems that random displacement activity has become incorporated into a stereotyped part of the courtship ritual. Mallards raise wing, thus revealing speculum and attracts attention to it by preening. The Mandarin Duck, in the same display, merely touches one large feather; never preens, but it seems apparent that the Mandarin display is evolved from preening behavior.

Mallard

Vocal displays

2009-12-08T09:28:00.000-08:00

No other group of vertebrates have developed auditory communication like birds: only primates are more complex. BIRD SONG IS THE DOMINANT NOISE IN FOREST.

Bird songs come from syrinx , which is found only in birds. It is located at the lower end of trachea and is analogous to our voice box. It is located where the bronchi come together but is not homologous to our voice box since there is no larynx and vocal chords. It works by syrngeal muscles surrounding junction and tympanic membranes on inner edges of bronchi. An extension of airsacs lies between tympanic membranes (see your text book). One result of this anatomy is that some songbirds can sing two songs at once!

After inhalation:
1) air sac fills with air between bronchi
2) tympanic membrane forced out all the way to other side of bronchus
3) pressure released from lungs
4) syrngeal muscles control how much air passes and vibrates tympanic membrane
5) syrngeal muscles exert a very fine control modulates vibration of membrane
6) the two tympanic membranes are independent in most passerines

Other sounds made by birds inlcude those from modified feather structures, like snipe tails and manakin wings.

Wilson's Snipe

Vocalizations

2009-12-08T09:26:00.000-08:00

Northern Mockingbird

You have bird songs and calls. Songs are reproductive vocalizations. Everything else is a call. Songs are usually seasonal. Calls are usually single or double notes. Songs are hormone controlled and manipulated, whereas the timing and pattern of calls are not. Calls usually serve an alarm or aggresssive function. Calls also contribute to social organization and are used in echolocation Songs attract mates and are rigidly controlled. Songs are usually more complex than calls and the delivery pattern usually quite fixed.

Vocalizations can be drawn out in a sonagram, which is a graph with sound frequency on the y axis and time on the x axis.

In general, Passeriformes are the best and most complex singers. The Northern Mockingbird is famous for its mimicking ability. I've even heard one mimic a train. On the other hand, storks don't call (they have no syrnx), but clap their bills instead. Generally, the duller the plumage, the more likely a bird is a good singer, since color functions much like song.

Some Song Research

2009-12-08T09:24:00.000-08:00

Ovenbird

Habitat (foliage density) influences song. Height is correlated with pitch, Cerulean Warblers are found high in trees and have a high-pitched song. Hooded Warblers and Ovenbirds are found low in the forest and their calls are louder and lower. Low-pitched pure tones travel better in dense vegetation. High, clear pitches do better in open areas; nightengales keep low in bushes where their buzzy song is less affected by wind and temperature.

Vocalization has motivation: aggressive = low and harsh; appeasement = high and soft. Why? Aggressive vocalization is replacement for combat. A bigger bird should tend to have a lower and deeper sound so you should advertise your bigness with that sort of call. On the other hand, baby birds sound high and attractive. High pitch = non-aggressive signal. Does this apply to human vocalizations?
Much research has focused on variability or organization or subunits of song:

Variability in Song

2009-12-08T09:20:00.000-08:00

Most species show variation or subunits of songs that they sing. It's common for birds to give up to 15 types or units of song. Some wrens can give up to 100 units which are repeated after different intervals. WHY? (It would seem that stereotypy would be favored.) Some theories include (and this shows how ornithologists think):

Black-throated Green Warbler

1) Black-throated Green Warbler = 2 distinct song types: 1 attracts females 1 repels males. But 100 different messages for Marsh Wrens? A lot of redundancy?

2) A great number of song types may be a trick to fool intruders--intruders think the territory if full of males! But birds do not call more variably at beginning of season and once intruders caught on, they would be favored since they would leave more offspring in a relatively empty habitat.

3) Sexual selection and competition for mates--FEMALES use # of song types as an index of males genetic fitness --functions like color.

4) A genetic marker--the more closely birds are related, the more similar the song type and make up.

a) Philopatric birds are aided in knowing birthplace.
b) Recognition of kin, so aggression reduced against kin = "kin selection"

Playback Experiments

2009-12-08T09:18:00.000-08:00

Indigo Buntings give a series of double notes. Researchers at Cornell jumbled up these notes and found:
1) order of notes not essential for species recognition.
2) rhythmic cadence and intervals also not essential.
3) parts of song that are constant within species are those that function for species recognition
4) parts that were constant within an individual but vary between individuals = species recognition
Birds react most strongly to calls by the same species. Less strongly to calls from different species. Even less strongly to species in different genera. Individauls react to same species call less with neighbors and more with strangers. One of my students played owl calls to illicit mobbing. She found that birds react most strongly to local owls and to those that eat small birds.

Territory

2009-12-08T09:15:00.000-08:00

Territory is any defended area beyond individual distance (usually against conspecifics)--vs. home range, which is an area an animal covers but does not defend. Some texts give up to seven types of territory, but I am content with four:

TYPE A: multipurpose mating, nesting and feeding resources contained in territory--MOST LAND BIRDS. Food evenly distributed; nests usually in center of territory.
TYPE B = mating and nesting but not feeding--starling and most seabirds. There is a gradient from B to C. Food not in nesting area (starlings nest in trees but feed in fields). Or food is or in clumps of fruits or seeds.
TYPE C = nesting only, not mating; only nest area defended--MOST ANY COLONIAL BIRD, LIKE PELICANS or BARN SWALLOW. Nesting sites limited, for example, Kittiwakes.
TYPE D = mating only = lek--RUFFED GROUSE, SAGE GROUSE , MANAKINS, or HERMIT HUMMINGBIRDS. This is the least understood territory type. Nest sites not limiting so perhaps females limiting.

What forces determine what type of territory a species maintains? (Territory types can vary: Song Sparrows in British Columbia feed outside their territories where they have an abundant food source; otherwise they normally have Type A territories).

Long-tailed Hermit

Feeding Flocks

2009-12-08T09:12:00.000-08:00

Cattle Egret

Birds feed: 1) solitary or in pairs; 2) single species flocks 3) mixed species flocks (3-20 species with few individuals of any one species).

(I might mention INTERSPECIFIC FEEDING ASSOCIATIONS: A species needs another organism for food either by necessity or opportunity -- rare in birds. Examples inlcude oxpecker or Cattle Egrets following cattle, antbirds following army ant swarms, honeyguides leading mammals to bee hives.)
Feeding flocks are not just feeding aggregations. Flocks are integrated, they act as group when danger threatens fly at same time, in same direction, etc.

Flock members can learn from one another. Great Tits in England learned to pull of milk can tops to drink the fat at the top of unpasturized milk. This behavior was documented as it spread through the population.

Other terms to take note of include: individual distance (others dare not intrude) and pecking order (usual in intraspecific flocks, reduces aggression-- everyone knows his or her place)
Crook studied Ploceidae in Africa. He found dispersion of good supply affects social organization. A gradient exists: evenly distributed food = solitary species; clumped food = single species flocks (mixed species unknown in plocieds). The correlation holds up fairly well except in some fruit and flower-eaters, which are solitary species. (Flowers are renewable but fruit isn't.)

What selective advantage could there be to flocking?

2009-12-08T09:10:00.000-08:00

Flocking can cost: large guillemot colonies can number in millions and take 200 tons of food a day from surrounding water. There are two hypothesis for flocking: 1) predator hypothesis 2) food hypothesis.

1. There is protection in numbers. You have more eyes flock to watch for predators. Clumped birds seem to be more difficult for predators to take--confuses predators (duck hunters know you have too aim at an individual in a flock). Wood Pigeons take more food in flocks and spend less time looking for predator. Many island forms, where there are no predators, don't flock.

2. Food is often in patches. Flocks can find more food/hr than a single bird and sharing doesn't cancel advantage. Flocking may stir up prey.

Galapagos finches flock while Hawaiian Honeycreepers don't--the difference is food! The finches eat patchily distribted seeds while the honeycreepers go for uniformily distributed flowers.

The two hypothesis probably go hand in hand.

In Costa Rica: solitary birds are: 1) terrestrial foragers in dense undergrowth, 2) hummingbirds which perch a lot, and 3) sentinel foragers that fly from perches. ALL HAVE LOW VULNERABILITY TO PREDATION. Single species flocks exploit clumped food, especially fruit. Mixed species flocks are found in forest upper stories, exploit evenly distributed food and are highly vulnerable to predators in canopy.

Flocking summary

2009-12-08T09:08:00.000-08:00

Form of advantage for flocking (and the type of group that benefits):

feeding efficiency
1. capturing difficult food flocks (pelicans)
2. flushing prey (cattle egrets)
3. efficient exploitation of indefensible food supplies (chickadees)
4. imitative foraging (chickadees)
5. information transfer (colonies and roosts)

anti-predator
1. "selfish herd effect" remaining in center reduces risk
2. increased vigilance--early warning
3. synchronous reproduction swamps predators
4. communal mobbing drives predator off
5. dilution effect--loss less of the total percent of prey population
6. confusion effect.

American White Pelican

Courtship and Mating

2009-12-08T09:00:00.000-08:00

Read about bowerbirds in your text, since I will not cover them here. Courtship is fairly descriptive natural history--it's amazing how much remains to be done. We watched Vermillion Flycatchers in Arizona court, only to read a paper on it the next year in a national journal. Their courtship had not been officially described when we watched them! I will limit this lecture to a discussion of pair-bonds.

There are 3 types:
1. monogamy (90% of birds) 1 male; 1 female. Usually for one season but sometimes permanent in long-lived species that are either nonmigratory or that winter together. Some albatrosses always come back to exactly the same spot.
2. polygamy (9%), Lasting pair bonds with a) polygyny = 1 male + 2 females; b) polyandry = 1 female + 2 males
3. promiscuity (1%) These birds are either random maters or form leks.

Once birds court, they then begin NESTING.

Northern Jacana

Evolution of Mating Systems

2009-12-08T08:57:00.000-08:00

Red-winged Blackbird

We assume all systems are products of natural selection, so all strategies provide optimal survival of young. We ought to be able to predict mating system if we know enough about environment.
If you are not monogamous, you must not need full attention of both parents. If you have 1 male + 3 females, then this must be better than 1 m + 1 f. Obviously (?) this increases the chance of success for the male (even at some loss of success in any given nest) so long as he can pull it off. But it is the female who does the choosing, since she makes the metabolic investment in gametes. So a 3 female territory must be an optimal situation for producing young out of each nest.

WHY polygamy? Studies of Red-winged Blackbirds show that males arrive first and set up territories. [Draw 2 boxes, male A with female; male B without.] WHY WOULD AN INCOMING FEMALE CHOOSE MALE-A? A's territory must be really much better than B's.

Within breeding populations, most polygnyous birds are marsh edge birds. Productivity is greatest at water's edge and female reproductive success depends on territory richness. Polygamy also occurs in hole nesters that use abandoned holes. Black-capped Chickadees' nesting holes are a limited resource and are nonrandomly distributed. A female has no choice if male's territory has 2 holes in it. (Chickadees are one of the few passerines that mate for life--of 200 Song Sparrows banded, only 8 remained with same mate the following spring.) Eastern Bluebirds are similar but studies show polygamous birds may have reduced reproductive success from females' fighting (males taken out experimentally).

Is polygamy a consequence of skewed sex ratios? or differential survival (what with males' being brighter)? This has not been documented.

Polyandry

2009-12-08T08:55:00.000-08:00

Polyandry is very rare in birds. Only jacanas are simultaneously so. Females hold "super-territories" encompassing several male territories. Males defend territories. A female may copulate up to 4 males on the same day, so they are probably never certain that they fathered the clutch the care for! Polyandry also occurs in Tasmanian Native Hens and tinamous. Spotted Sandpipers (up to 4 males in succession) and dotterals are SERIALLY POLYANDROUS.

Polyandrous FEMALES are often prettier but sex role changes do not necessitate polyandry--Wilson's Phalaropes are monogamous.

Greater Rheas actually a mixture of polygny and successive polyandry. Males compete for small flocks of females. Dominant ones win harem. The male makes a nest and each female lays several eggs in it (average 28 eggs, record 62!). The females then move on to new male! The males incubate and guard precocial young.

No good theory for polyandry has been proposed. Why is it so rare? A salient feature of polyandrous species is that it MUST NOT BE DISADVANTAGEOUS FOR MALES, so young must be independent at hatching.

Nesting

2009-12-08T08:48:00.000-08:00

What is a nest?

Only one living bird does not incubate: AUSTRALIAN MEGAPODES (moundbuilders). They dig pits and throw sand on top. An egg chamber lies on top of pile of organic matter. The fermentation of organic matter produces heat. The megapode can control the temperature of the egg chamber by bringin in new or taking out old organic matter. Is this left over from reptilian ancestry or independent development?

A few birds build no nest, by any definition, nothing. Brood parasites are an example. The Galapagos Albatross and some penguins don't build nests. Fairy Terns lay single egg in a tree fork. The chick is born with oversized feet--if they fall, the parents ignore them.

Most other birds build nests--simple to complex. Complexity proportional to: time investment (= metabolic rate), consciousness (more complex = more conspicuous); and accessibility to predators (the more complex, the more inaccessible)--in areas with few predators = less well hidden.

Nests in the tropics are hidden and better camouflaged. Nests on islands are often conspicuous. Nests often provide protection from weather. In the temperate zone, where it is cold and windy, nests are deeper, thicker, lower in trees (?), In deserts, look for domed nests, few open cups.

Here are the next topics to be covered:
TYPES OF NESTS
COOPERATIVE BREEDING
EGGS
INCUBATION
YOUNG
BREEDING SEASONS

Galapagos Albatross

Brood Parasites

2009-12-08T08:46:00.000-08:00

Cowbirds have young that are usually bigger than host young and out competes them. Many parasites are able to retain egg in oviduct until host can be found, and this may explain why parasite more advanced. In European Cuckoos, the eggs resemble most common host in area--usually fairly specific in host selection (one of our cuckoos occasionally fails to make own nest).

Females brood parasites usually destroy 1 host egg. Occasionally whole nests are destroyed, causing the host to renest. Young wydah's gape patterns (and feeding postures and calls match those of host. Wrong gape pattern wont be fed). Pied-crested Cuckoo lay thick-shelled egg from above nest this damages one of host's eggs. Young parasites may eject host eggs or young or actually murder them (honey-guides have sharp mandibular hooks). In the Indian Koel (a cuckoo), male approaches House Crow nest calling loudly. When the incubating crow gives chase, the female koel slips in to lay egg. Some parasites have protrusible cloaca so they can lay eggs in holes that are too small for the adults. Others lay eggs very quickly (1-2 seconds apart in European Cuckoo).

The evolution of parasitism: a) take over nest of other species but still taking care of own young (Bay-winged Cowbird); b) leave host to rear young or intra-specific brood parasitism, such as in starlings and tree swallows.

Yellow-billed Cuckoo

Types of Nests

2009-12-08T08:44:00.000-08:00

SCRAPES--shorebirds, terns, skimmers, & nighthawks use scrapes in open situations.

BURROWS-- birds probably used natural burrows and later moved to excavated burrows. Advantages of ground burrows include: microclimate stable, nest stable, predator protection. Disadvantages are that predators, once they find them, can easily get at them. On the other hand, birds in tree burrows escape flooding. But they have disadvantages. They must compete for tree holes. It takes time to make both kinds of burrows. Hole nesters usually enjoy a 66% success rate in fledging whereas open cup nesters have only a 55% rate.

PLATFORM NESTS--primitive: line scrape with vegetation or, in the case of waterfowl, line nests with own feathers. Cormorants and herons build platforms in trees. Grebes build floating platforms, anchored to vegetation. One South American coot, Horned Coot, piles pebbles and makes own island for its terrestrial platform nest (over years, pebbles can weigh up to ton).

CUP NEST--probably evolved from platform nest, most common today. Robin = statant nest, support mainly from below. Barn Swallow = adherent nest, stuck on side. Swifts use saliva to glue nests to edges of chimneys. Ovenbirds build cup on ground. Marsh Wrens make a ball entered by small hole. Other "cups" are suspended from top by branches vireos from rims at tree forks = pensile nests. Finally, orioles = pendulous nests, that hang from branches.

COMMUNAL NESTS--some weavers basically build apartment houses (look for a picture on the Internet).

(Mention should be made of Smooth-billed Ani: they lay their eggs in each other's nests = a step towards parasitism? Each nest is separate though.)

Black-tailed Gnatcatcher

Cooperative Breeding

2009-12-08T08:40:00.000-08:00

Helpers at nest are occassionally encountered. The costs of this activity to the breeder include: 1. more birds in territory eat more rearing parents' offspring, demands time and energy and potentially produces more exposure to predators. 2. helpers may be incompetent. 3. helpers may compete with breeders for right to breed.

On the other hand, benefits inlcude: 1. Assistance in rearing young experience in rearing young; parental genes' survival is enhanced (kin selection). 2. if parent dies, other gets help access to resources in parents' territory. 4. help in territorial defense. 5. increased foraging efficiency detection of predators, etc.

I should mention in passing that some small birds in tropics protect nests by always building near wasps or ants (Yellow-rumped Caciques). The advantage to the bird is that wasps kill avian bot flies. The birds may protect the wasp nests from intruders (?). Hornbills protect themselves from monkey predation by sealing females into nest cavity, fed by males. Females and young break out when fledged.

Yellow-rumped Cacique

Eggs

2009-12-08T08:38:00.000-08:00

All birds lay hard-shelled eggs--none give birth to live young because of weight problems. Try to find a diagram of the female reproductive system and what happens where and when (it takes 24-48 hr. = follicle to vagina):

Facts to note are that fertilization occurs in the ovary. When the follicle ruptures, the ovum starts down the oviduct and consists only of yolk and embreyo. Egg white is added in the oviduct. Albumen and the egg membrane are added in the isthmus. Finally in the uterus the egg shell and pigment are added.
All this takes a tremendous amount of energy (?) (classically assumed, anyway: time of molt may actually be much more critical). (Never hassle molting chickens--they are liable to go into shock).

If young Blue-footed Boobies leave the guano circle around the "nest," the young are ignored by the parent and the young starve.

More about eggs

2009-12-08T08:36:00.000-08:00

A clutch can equal more than a mother's body weight. One egg is laid at a time, often separate fertilization is needed. The smaller the bird, the relatively bigger the egg.

EGG SIZE, SHAPE, AND COLOR

In general, precocial birds' eggs will be a higher percent of their body wieght than will be the eggs of altricial birds. The egg of an American Golden Plover is 50% bigger than a Western Meadowlark egg. Most bird eggs are chicken-shaped. However, some cliff nesters have very pointed eggs so they roll in tight circle.

We assume WHITE EGGS are primitive, since that's the way reptiles are (according to oologists). Eggs are really species specific, yet adaptive significance of egg color is obscure. highly camouflaged eggs (ground nesters) = browns and grays; open cup nesters in trees = blurry shadow marks on blue or white backgrounds; hole nesters = white eggs; and I've mentioned the variably colored eggs of European Cuckoos.

American Golden Plover

Clutch Size Patterns

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A clutch is the number of eggs in a nest. Clutch size is variable, 1-20, but not random due to selective reasons. Clutches vary WITHIN SPECIES and WITHIN SPECIES GROUPS.

We have seen that different groups of birds and even different populations have characteristic clutch sizes. WHY? How did these evolve? High mortality requires fairly large clutches (to offset mortality). Birds with low clutches presumably suffer less mortality and higher clutches would lead to overpopulation.

Why do birds have low clutch sizes then? Why not just go for the maximum number? Low clutch size is not a mechanism to avoid overpopulation, however, not group selection. Few eggs must be the best way to achieve OPTIMUM SURVIVAL. Advantages of small clutch size include that it does not overly tax food supply and it results in healthier nestlings that develop quicker (each get more food).

Horned Lark

Within Species Clutch Size Patterns

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a) AGE OF FEMALE--1st year females have slightly smaller clutches than all others. For example, European Starlings lay on the average 4.45 eggs the first year and 5.60 eggs in subsequent years. Most birds don't live much longer than two years, but they don't usually lay more and more. Black-legged Kittiwakes lay 1.8 the first year, 1.9 in years 2-3 and 2.4 in years beyond 3.

b) SEASONAL--clutch size decreases through season. Field Sparrows lay in May 3.77 eggs, in June 3.69, in July 3.14, and in August 3.00. These numbers, of course, are averages. 0.14 of an egg is kind of messy.

c) ANNUAL--clutch size varies from year to year, depending on severity of season and food supplies. Some examples, followed by minimum and maximum per year are: European Starling 6.4 -7.5; Red Grouse 6.1- 8.1; Common Eider 4.72- 5.44; The European Swift lays 2 or 3 eggs, smaller selected for during lean years, the larger selected for in good years.

d) POPULATION DENSITY-- The Great Tit lays 2 eggs in times of high density, 2 more in times of low density, so there can be a 4 egg difference.

e) FURTHER INLAND PROPORTIONAL TO CLUTCH SIZE--Song Sparrows have the largest clutches in the center of the country (3-6-3). WHY? Lower life expectancy less rich environment harsher climate must be compensated for.

f) LONGITUDE--Away from equator, clutches increase. In House Wrens in: Amazon = 2, Central America = 3, Mexico = 4, southern USA = 5, Canada = 6.

h) ISLANDS PROPORTIONAL TO CLUTCH SIZE-- passerines on islands = 2-3, on mainland = 4-5. WHY?

Promiscuousness

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Wire-tailed Manakin

Basically, leks, Food not randomly distributed or at least not defended (super abundant). The species are nomadic and have aggregation points, often traditional. The females raise and feed young; mainly fruit-eating birds. Males display together and the females come in. A few males may inseminate most females--One male White-bearded Manakin managed 73% observed copulations; in Sage Grouse: 75% copulations with 10% of males.

Other birds that use leks include flower sucking: Phaethornis; fruit-eating: manakins (except insectivores), cotingas, and birds-of paradise; seed-eating: grouse; and insect-eating: Buff-breasted Sandpipers and Ruff.

Its been suggested that insects in the Arctic are patchily distributed, so Arctic nesting sandpipers make leks near concentrations of insects.

David Lack did some interesting work with Starlings

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He banded baby starlings in the nests and then tried to recover them after they fledged.

ï¿½clutch size	# nests	% recovered 3 mo. later	productivity (= relative % recovered
1	65	0	0
2	164	1.8	3.7
3	426	2	6.1
4	989	2.1	8.3
5	1235	2.1	10.4
6	526	1.7	10.1
7	93	1.5	10.2
8	15	0.8	6.4
9	2	0	0
10	1	0	0

Other studies have shown that young starlings with optimum body weight come from nests with clutch sizes around 5.

SO WHY DON'T ALL STARLINGS LAY 5 EGGS? WHY DOES SURVIVAL DECREASE IN SMALL NESTS?

European Starling

So Why Don't all Starlings Lay 5 Eggs?

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European Starling

Different habitats support different food supplies; rich habitats can support starlings with bigger clutches. Genetics are involved. Conservative birds may be best in lean years big clutches best in good years--both will be selected for in overall population fitness
.
WHY DOES SURVIVAL DECREASE IN SMALL NESTS?

1) Perhaps low clutch size is a reflection of poor habitat?
2) physiology of nests--thermal advantage in cool climates for bigger broods (the babies keep each other warm)--indeed, larger nests may need less food to thermally maintain young. On the other hand, large broods may get too hot in tropics-and there are few big ones there.

Clutch size variation within species groups

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a) BIG BODIES PROPORTIONAL TO CLUTCH SIZE--In grouse, as you move from small to large species, you move from clutch sizes of 13.7 to 11.4 to 11.3 to 9.0. Similarly in hawks, you move from 4.1 to 4.1 to 3.2 to 2.4. In wrens, you move from 6.8 to 6.5 to 6.0 to 6.0 (the numbers represent average clutch sizes for various size classes of birds).

b) HOLE NESTERS HAVE MORE EGGS THAN NONHOLE NESTERS IN SAME FAMILY. In British passerines, open cup nesters average clutches of 5.1 while hole-nesters average 6.9 eggs. WHY? A cup may be too conspicuous--all eggs in 1 basket?

c) HABITAT--forest birds have smaller clutches than birds that nest in meadows. There is likely more food in meadows.

d) SOCIAL STRUCTURE-- no pattern! This is kind of surprising. One reason may be that, with no males, females can still fend for young.

Wood Thrush

Theories of Clutch Size

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1) Reproduction adjusted to match mortality. This is GROUP SELECTION -- "you don't want to overpopulate. " It becomes a matter of altruism vs. cheaters. Cheaters should win and you can't predict birth rates.

2) David Lack: natural selection will favor those that have most young, therefore, the clutch size will tend to be as high as possible. Thus clutch size should be proportional to food availability.

Golden-crowned Kinglet

Trends in clutch size

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1) age of female: older better at getting food

2) seasonal, variability of food supply

3) annual, food supply varies

4) population density, more competition for food in high populations

5) latitude, more daytime in north--you have 20 hours of daylight in Hudson Bay where there are few competitors, both avian and other. Tropical rainfall may further reduce time for clutches. The tropics lack seasonal burst of productivity. Recent research indicates north more productive than the tropics.

6) longitude: inland much more seasonal, so has a bigger blip in productivity

7) islands have lower clutches--islands are less seasonal than mainland and have fewer predators. Islands are also more densely populated

8) body size --big birds take bigger prey that's scarcer than smaller prey so they can't bring in food as fast???

Some experimental work suggests Lack is right when he suggested that food availability is the most important variable affecting clutch size.

Rufous Motmot

Lack might be right

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Crossner manipulated brood sizes in field. He had two groups, one natural and one with an unlimited food supply. He found the body weight of fledglings was more or less equal in those with unlimited food, but highly variable in the other group.

OTHER RESEARCH HAS SHOWN THAT BIRDS NORMALLY PRODUCE SLIGHTLY LESS THAN THE "OPTIMUM NUMBER".

Barn Owl

Incubation

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This lasts from laying to hatching (after hatching is called brooding). The eggs have to be kept warm for enzyme matinence. The size of the egg and the cold resistance of eggs proportional to time kept covered. The more the eggs are covered, the faster the development of the embryo.

The BROOD PATCH is a featherless area on the belly. It is highly vascularized -- applied directly to eggs. Birds will turn eggs to distribute warmth. Incubation usually starts only after whole clutch is laid to insure synchronous hatching. In areas with sparse, or unpredictable resources, ASYNCHRONOUS HATCHING is favored so 1 or 2 young will survive, and the smaller chicks will starve.

Incubation time ranges from small passerines (= 10 days) to albatross (81 days), with the average being 12-14 days. There are five factors that affect incubation time. ALL 5 FACTORS MUST BE TAKEN INTO ACCOUNT.

Galapagos Pelican

Factors affecting incubation time:

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Three-toed Woodpecker

1. Size proportional to time. Generally larger birds incubate longest.

2. State of development at hatching. Even in altricial birds, limited resources produce smaller eggs that hatch quicker.

3. Predation rates. With high predation rates, there is selection pressure to get out of the nest as soon as possible. Hole nesters incubate for shorter times than do open cup nesters. In Costa Rica, Skutch found that birds that nested low to the ground incubated for 11-13 days, open cup nesters in trees incubated 14-20 days, while hole nesters took 17-24 days. Each type of nest on this less has a correspondingly lower vulnerability to predation.

4. Availability of food--most birds just can't afford to spend all their time on the nest.

5. Environmental temperature--the colder it is, the slower they embryo growth rate. Early spring clutches take longer to hatch.

Breeding Seasons

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If reproductive success is correlated with food supplies, breeding should occur when food supplied are highest--as indeed they do. Most birds also avoid breeding and molting at the same time, since both these times are probably critical energy consumption times. Almost all birds are seasonal. How do birds know when to breed? There are ULTIMATE vs. PROXIMATE CONTROLS.

Field Sparrow

Ultimate Factors

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The reason for adaptations to environmen.

1) FOOD is by far the most important ultimate factor. In the Blue Tit, the male provides up to 40% of the female's total food requirements through COURTSHIP FEEDING. In Arctic Terns, the more food the male brings, the earlier egg-laying occurred and the larger the clutch. American Goldfinches feed young seeds and consequently breed later than seedeaters that feed young insects (most others). Eleonara's Falcon breeding corresponds with peak of fall migration. African raptors breed before grass covers rodents during summer rains. Wood Storks breed in summer when fish are concentrated in pools (although fish are not necessarily most abundant then).

2) COMPETITION. The competition for hole nesters is so severe that they nest when less competition for holes-- early in nonmigrants. Black-capped Chickadees in South Dakota begin singing in January or February. Different populations of seabirds often breed at different times, because of competition for cliffs or burrows. North American migrants to South America may affect resident birds, reducing food availability.

3) NESTING CONDITIONS--riverbank nesters have to wait for dry season when water is down.

4) PREDATION PRESSURE--driver ants in Africa are seasonal and cause seasonality in birds.

5) WEATHER--controls food and nesting conditions. Heavy rains avoided by tropical birds. Cormorants in Lake Victoria avoid windy season.

Black-capped Chickadee

Proximate Controls

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Two general types, each sharpens birds' physiology more and more:

1) Endogenous rhythms--birds in labs still show internal rhythmic cycles of breeding and molting, but cycles won't continue forever, they must be readjusted by:

2) Zeitgeber, time-giver, resets endogenous rhythms. This is usually photoperiod but can be rainfall. For example, daylight increases, hormones are released by hypothalamus, these affect the anterior pituitary, which in turn releases hormones that affect the gonads. The eyes not needed needed in this process. The pineal gland may play a role.

You can artificially induce breeding, except during what's called REFRACTORY PERIOD. You can't induce breeding from end of season until midwinter. Is this adaptive (Indian Summer would be a foolish time to begin breeding) or the result of physiological drain?

Birds can respond to minor variations in environment--temperature (hot or cold), insect abundance (rains in tropics) --all can delay breeding time. In the Arctic, jaegers and Snowy Owls feed on lemmings that vary greatly in numbers. If the visual presence of lemmings is absent, both won't breed! Appearance of habitat may also affect breeding. Ruffs want short, light green fields, otherwise fields will be too high by breeding time.

A number of seabirds are acyclical or have a shorter than 12 month cycle--Sooty Terns breed every 9.6 months. This allows birds to breed and molt and breed again in less than a year, resulting in 4 broods every 3 years rather and 3 on an annual cycle.

Sooty Terns

There are two types of young

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PRECOCIAL--are covered with down; eyes open, alert; legs strong, can walk in few hours; nest on ground, almost never in trees.

ALTRICIAL-- naked, can't regulate temperature; eyes closed at hatching; weak, can't stand up; mouth lining variable, often conspicuous, bright; nesting is variable, all tree nesters are altricial except the Hoatzin.

There is really a gradient from precocial to altricial.

Northern Waterthrush

The Precocial -- altricial gradient

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(If you need to, look up to which birds these family names (ending with idae) refer to your text or field guide.)

1. completely independent of parental care (Megapodes; mudnesters)
2. follow parents but feed selves (Anseriformes, Scolopacidae, Charadriidae)
3. follow parents but are shown food -- parents peck at food (quail, grouse)
4. follow parents that feed them (Rallidae, Podicipedidae)
5. semiprecocial: down-covered, open-eyed, but stay in nest (Laridae)
6. semialtricial: down-covered, open or closed eyed, can't walk but are fed by parents
7. 100% altricial
factors causing gradient:
1. Predation pressure: precocial nesters are ground nesters
2. Location of nest: tree nesters or cliff esters don't want precocial young
3. Type of food: precocials are ground feeders parents and young feed together if parents have to go away for food, altricial young will be favored. (Many ground-nesting passerines must be fed in high grass, so altricial.)
4. Phylogenetic background: some ground nesters are altricial (ovenbird, waterthrush) but these are relatively recently evolved from genera with altricial young.

Cliff Swallows

Migration

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Ring-necked Duck

I am mostly going to talk about navigation and physiology of migration. It's not uncommon for passerines to cover 1000 km/day, therefore, many Canadian migrants probably make their first landfall south of South Dakota after fueling up in the forests of eastern Nebraska. We need adverse weather to bring them down here. This is similar to what happens in Louisiana where you have what is called a Coastal Hiatus. In good conditions in the spring, birds take off from the Yucatan at dusk and make landfall in Louisiana well north of Baton Rouge. In bad weather, the birds crash down on the Louisiana coast. After several days, they take off and probably make their next landing well north of Louisiana. Therefore, much of the inner coast of the state sees few migrants, unless a cold front goes by just when the birds are overhead. In most of the USA, a sunny fall is not good for bird watching.

What is migration? Migration implies a return trip seasonally. The record holder is probably the Arctic Tern = 10,000 miles from the North to the South Atlantic. Penguins walk, some geese begin walking because they molt all their flight feathers at once. There is also elevational migration, up and down mountain ranges.

WHY DO BIRDS MIGRATE?
HOW DO BIRDS ORIENT?
STUDYING MIGRATION
THE PHYSIOLOGY OF MIGRATION
WHAT ABOUT BIRDS THAT DON'T MIGRATE--HOW DO THEY COPE?

Why do Birds Migrate?

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SURVIVAL WILL BE ENHANCED. A seasonal shortage of food is the main factor. Weather, per se, is probably not so important. Partially migrating species can be held for the winter in the North. Small birds can withstand great drops in temperature, like up to 140 to 60 degrees F.

The distance migrated varies even within species, as I have said, some birds are partially migratory. In these cases, the young of migrants tend to be migrants also (so if something happens to the nonmigrants, the population can be replaced. Birds probably migrate just far enough to assure their survival. Shorter distances or longer distances must be disadvantagous. Likewise, migrating at all must be a tradeoff to the dangers of trying to survive the winter.

The dangers of migration include getting lost, storms, energy loss (exhaustion). Blackpolls migrate from Canada to Ecuador. They gain half their body weight in fat.

In partially migratory species, its the females and young that migrate: dominant, territory-holding, males tend to stay put--the cost of migration must be less for migrants than if they did stick it out.
Eruptive species: food supply varies markedly from year to year. What happens with many winter finches is that they feed on pine seeds. The trees go through roughly a four year cycle in seed production. When you have lots of seeds, you have lots of finches. The next year, with few seeds, you have a lot of hungry finches pouring into the United States from Canada. Examples of winter finches include Red Crossbills and Purple Finches.

Migrants usually build up fat reserves--young Manx Shearwaters leave British nesting grounds 50% heavier than adult normal weight and go to Brazil and Argentine waters. One banded bird made it in 14 days (570 km/day). Sanderlings build up enough fat reserves for a 2000 km trip!
You might try Googling bird migration and see what you come up with.

Pine Siskin

Migration Theories

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NORTHERN HOME THEORY --Northern residents retreated in front of Pleistocene (or earlier) glaciation--after glaciation the birds returned as far north as possible each summer.

SOUTHERN HOME THEORY--Birds originated in tropics. Population expansion and competition drove those that could survive, north (and south) where, indeed, they did find incredibly rich resources and lots of time to exploit them!

All Northern Wheatears winter in Africa, even those in western Canada cross Asia! Wouldn't it be easier to winter in South America or is it not worth the risk to break with tradition? We do have a couple of Wheatear records in South Dakota.

American Tree Swallow

How do Birds Find their Way?

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There are five main cues. The evidence is fairly solid that not just one cue used--the cues serve as dual or auxiliary systems

1) TOPOGRAPHY--mainly daytime migrants. Hawk Mountain is a famous example. Raptors follow the south-west to Northeast mountain ranges. Because they really want to be going more or less south, they pour through passes rather than going over the mountains. Thousands of hawks can be seen at Hawk Mountain during a single day. Certainly the final stage of migration must be dependent on topography. Although homing pigeons in Boston seemed to be following interstates, they do not need sight to find their way home: researchers put frosted contact lenses over their eyes and they still found their way home!

2) POSITION OF SUN--birds might have an internal clock (we have one too, that's why we get messed up traveling). At a given time of day, the bird might know where the sun should be. The bird then travels in that direction is the sun isn't where it ought to be.

3) STARS--Researchers in planetarium studies can shift the night sky, and orientation shifts. Birds mostly cue on NORTH STAR and those rotating nearby. Note that 1000-2000 years ago, star positions were not where they are now, so birds must be able to adapt to celestrial changes. Young raised in isolation oriented correctly BUT MUST BE RAISED OUTSIDE. Interestingly, 99% of lost birds are juveniles. In wood warblers: the farther from N-S route is the normal migration route, the more likely they are to show up in California. Most of these go southeast in the fall, so perhaps landing in California means they have a mirror image of proper migration route.

4) MAGNETIC FIELD--circling the earth, it can be used by several species. In disturbed fields, birds don't orient properly. How do they perceive the field? Some fish have electro-receptors, but birds? In any case, birds still orient in a cueless cage but, put a steel shell around cage, and you get randomness. If you artificially alter magnet field in sky-opened cage, you CAN cause alteration of orientation. Recently magnitite has been discovered in birds' inner ears, and this may explain their sensitivity to the magnetic field.

5) POLARIZED LIGHT: could be used if birds perceive it.

6) OLFACTION: birds might not be all that bad at smelling--some new data suggest pigeons may home by olfaction!

Try Googling any of these subjects for more information.

Bonaparte's Gull

Studying Migration

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Techniques for studying migration include radar, transmitters, moon watching and banding. A transmitter-fitted Whooping Cane took off from Montana, flew around the Black Hills of South Dakota, and made landfall in Nebraska.

Banding returns tend to be poor--001% for small birds. Some duck hunters don't even report bands, since they are afraid of government interference in their sport. The Fish and Wildlife Service has had to resort to award bands, worth varying amounts of cash. Hunters are the weak link in wildlife management.

In moon watching, you train telescopes on the moon. By counting bird shadows, you can estimate numbers in the air and direction of their migration. George Lowery conducted a nationwide survery of migration during four nights in October.

The images of birds by radar is often spectacular and warns of danger to planes.

Banding Cliff Swallows

The Physiology of Migration

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White-throated Sparrow

The White-throated Sparrow winters in southeastern US, breeding in across Canada. During early spring, it stores large amounts of fat as an energy source during flight. Reproductive development occurs during spring. Following the June breeding, gonads regress and remain small until next spring. These events (fattening and gonad size increase) and migratory restlessness and orientation towards north or south are ALL AFFECTED BY PROLACTIN FROM PITUITARY and CORTICOSTEROIDS from the Adrenal cortex.

A. H. Meier injected corticosteroids into White-throated Sparrows at time zero. Prolactin given at 12 hr. results in: rise of fat stores, rise in gonad size, rise in migratory restlessness and a rise in locomotor activity towards north (= spring migrant). Prolactin given at 4 hours results in arise in fat stores, rise in migratory restlessness, NO gonad increase, and an orientation to south (= fall migrant). Prolactin at 8 hr. decreases fat stores, decreases locomotor activity, and decreases gonad weight (= winter bird).
This does not explain how the bird knows which way is north or South.

What about birds that don't migrate?

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ADAPTATIONS TO TEMPERATURE EXTREMES

Unlike poikilotherms, birds' body heat allows them to maintain constant body temperature, thus they are HOMEOTHERMS. Poikilotherm body makes heat too, but metabolic rate low and what heat is produced is quickly lost, thus it depends on environment for body heat.

HOW DO HOMEOTHERMS MAINTAIN CONSTANT BODY TEMPERATURES?

1) control heat loss by insulation (fur, feathers).

2) high energy metabolism--they can expend internal energy to increase heat production. You can get a broad, U-shaped graph of oxygen consumption in warm-blooded animals. On either side, lots of energy is required to maintain body head. Across the broad middle of the graph, you have a THERMAL NEUTRAL ZONE (17-40 Degrees C). This is a range of temperature in which energy is not expended to maintain body temperature. The bird is able to use behavior or insulation. Beyond this zone, energy is expended.

At the LCT--the lower critical temperature (where curve starts going up)-- a bird needs to produce heat, it: metabolizes fat, shivers, eats more food and requires additional energy sources. At the UCT--upper critical temperatutre (where curve starts going up)-- an animal must produce water for evaporative cooling or pant to increase air of respiratory surfaces.

EVOLUTIONARILY birds: 1) in cold, lower LCT; 2) in heat, rise UCT and 3) change slope of O2 consumption curve to expend less energy, they DAMPEN UPWARD CURVES.

Hairy Woodpecker

Adaptations to Heat

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Most birds seldom face too hot a temperature. A bird's body heat ranges from 39-42 degrees C. Birds don't sweat, so must lose heat by passive conductance to outside.

1) panting--increase air flow over respiratory surfaces. This requires energy.

2) gular fluttering--has been described in 150 species of birds. Pelecaniformes' loose, thin pouch at floor of mouth can flutter with little energy to increase airflow in mouth. Gular pouches weigh little and show resonant properties. (Panting increases with heat while gular fluttering remains constant regardless.)

3) urinate on legs--done by storks and turkey vultures, this obviously increases evaporation rate on legs.

4) increased efficiency of water conservation--(e.g., kidney efficiency improvement)--desert birds (like Roadrunners) have longer loops of Henley than do non-desert ones, which may lack them. Look these up if you don't know what they are or how they work.

5) behavior. Birds often dangle their legs behind them as they fly in high temperatures. Sandgrouse: daily activities correspond to cooler temperatures; feathers absorb water, which can be transported to their young. Most desert passerines thermoregulate behaviorally. Magpies face white parts of their body towards the sun when then are hot, black parts when they are cold.

6) countercurrent exchanges are lacking when birds need to loose a lot of heat. Maximal heat loss is through feet (like Snowy Owls).

Double-crested Cormorant

Adaptations to Cold

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1) Plumage--a bird can increase insulating layer. Northern birds have higher densities of feathers than do southern ones. Individuals show seasonal differences. The House Sparrow molts after breeding season and the winter plumage weighs 30% more than the summer one. Thus the bird shifts LCT down to 0 degrees C. Snowy Owls have a very heavy plumage: LCT = -10 C. Emperor Penguins breed in the winter when the average daily temperature is -25 C.

2) Counter-current exchanges. Look this up in a General Biology book. Extremities are sources of heat loss, especially for herons and gulls. They remedy this by running warm arteries close to cold veins.

3) Fat storage--acts as insulation, stores energy and yields higher energy than proteins. The Emperor Penguin increases its body weight with fat --50% is burned off in 2-3 months while the MALE incubates eggs 65 days without food.

4) Shivering--spasmodic muscle contraction to release heat and seen most often in cold climates.

5) Decrease surface/volume ratio. BERGMAN'S RULE: body size increases as you go north. Birds don't really follow ALLEN's rule with smaller extremities with a gain in latitute (perhaps because relatively little heat is lost through extremities, compared to mammals), but look at penguins' small flippers and wings!

6) Behavior--birds in cold roost in cavities or under other surfaces like snow. Birds often aggressively will huddle (many textbooks have photos of creepers huddling). Birds will forage on leeward side of tree in wind and they will sunbathe.

7) Torpor--a reduced metabolic state. Torpor has been discovered in a few birds: Swifts, goatsuckers, and some swallows. Google torpor on the Internet and see what you can come up with.

Snowy Owl

feathers

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Feathers are horny (keratin) structures produced in skin follicles. We don't know much about origin of feathers, since they appear full-blown in ARCHAEOPTERYX. The fact is that feathers may represent the results of only one or two mutations on the part of reptilean scales.

Feathers usually grow in FEATHER TRACTS with spaces between called APTERIA, where there are only scattered feathers. Penguins and screamers are completely feathered birds. Adult ostriches are completely feathered but their embryos have feather tracts, so perhaps being completely feathered is a secondary characteristic in birds.

Look at the diagram of a feather in a textbook. The vanes zip up like a host of tiny zippers, which is what happens during preening.

Black-crowned Night Heron

Kinds of Feathers

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You might look in a textbook to see what these look like.

afterfeather-- grouse and pheasant; increases insulation.

contour feather (these include flight feathers)--can be amazingly modified.

down feather--increases insulation. Two kinds exist: natal = short calamus with long flexible barbs that don't interlock, gives protection; adult = has rachis, serves as insulation.

semiplume--intermediate between down and contour feather with no interlocking barbs, provides insulation.

filoplume--"hairs" on domestic fowl after plucking, has long rachis with small trace of vane at top. It is found on napes and backs of some passerines. The function is unclear. Sensory?

rictal bristles--along the edges of birds' beaks. May help in flycatching.

powder down--strangest of all feathers, these continually grow, breaking off to form talcum-like powder. The exact function is unknown. They occur singly or in patches and can be a taxonomic tool on herons (where may remove fish oil): bitterns = 2; typical herons = 3; Boat-billed Heron and some Tiger Herons = 4. Powder down also rarely occurs in passerines.

Bare-throated Tiger Heron

Molt

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Molt has a complex terminology. Sequences of feather replacement are quite variable although usually quite stereotyped for any one species. Some cranes keep feathers for two years, but most birds molt all feathers annually. A total replacement is termed a complete molt, which takes weeks to several months and is very energy costly. Most north temperate birds do a complete molt in late summer or early fall (Tyrannidae and Hirundinidae delay molt until on winter grounds)

Many species molt only once a year, others molt twice. The number of feathers molted the second time varies greatly (= partial molt). The Bobolink is one of the few birds to have two complete molts, basic and alternate. A very few birds have three molts a year, one complete and two partial.

Bobolink

Molt Terminology

2009-12-07T22:40:00.000-08:00

Molt has a traditional terminology and a new terminology. The traditional terminology did not always work well outside the Northern Hemisphere and does not take into accounts places where there is no winter, but, say a dry and a wet season. Also, many species don't breed in their first nuptial plumage. The new terminology, developed by Humphrey and Parks, is increasingly being used to describe molt.

traditional terminology / new terminology

natal down / natal down
postnatal molt / prejuvenile molt
juvenile plumage / juvenile plumage
post juvenile molt / first prebasic molt
first winter plumage / first basic plumage
first prenuptial molt / first prealternate molt
first nuptual plumage / first alternate plumage
first post nuptial molt / second prebasic molt
second winter plumage / second basic plumage
etc.... etc...

Great Crested Flycatcher

Color Polymorphism

2009-12-07T22:30:00.000-08:00

Color polymorphism is when you have two or more distinct, inherited (= genetically based) plumage types with non-continuous variation. In other words, you have birds with two distinct color types with no blending inbetween. This is obviously not a subspecies since not geographical (?) It often occurs in mixed clutches. The adaptive bases for polymorphism is unclear. Most polymorphic birds are raptors: hawks, owls, jaegers. 95% of polymorphism involves a dark and light phase.
Paulson hypothesized that diurnal birds undergo selection for variation for its own sake: it's harder for prey to learn what you look like: sort of a reverse "search image." Some evidence supports this theory, polymorphism in hawks related to those with visually acute prey. Generally insectivorous and snail-eaters aren't polymorphic. Australian Goshawks not polymorphic where they don't feed on birds. And most polymorphism is ventral.

ON THE OTHER HAND: prey key on silhouettes not colors. And the rarer morph should have adaptive advantage and therefore should increase: no evidence for this. Owls often show polymorphism and they are nocturnal.

Jaegers are predatory. There are three species in the Arctic: Pomarine (feeds on lemmings), Parasitic (birds), and Long-tailed (insects) little polymorphism. The rare white morph in Iceland is more successful than the others, so why don't they increase? PERHAPS DARK AND LIGHT MORPHS GENETICALLY LINKED TO SOMETHING ELSE.

Screech Owls' gray form is most common everywhere but least common in N and S part of range. Red is most common in mid latitudes. Turns out that more red birds die in severe winters: in lab below 5` centigrade, red birds died while gray birds needed less food.

Eastern Screech Owl

Colors in Birds

2009-12-07T22:25:00.000-08:00

There are two ways that birds produce color. The first is by pigments, which include melanin, lipichromes (reds, yellows, oranges), carotenoids (reds, greens, browns), and porhyrins. The second is through ultrastructures (= blues) (black, dull yellow, brown). If you place a Blue Jay in a blender, all you get are fragments of brownish feathers.

We have no predictive theory for adaptive coloration: knowing habits, we can't predict color. Of course, color plays roles in species and sexual recognition.

Common Redpoll

Functions of Colors

2009-12-07T22:20:00.000-08:00

White-tailed Ptarmigan

1) predator defense via concealment.--Relative to other vertebrates, birds tend not to match background color because a) they're mobile, b) sexual selection (birds are visible to attract mates), and c) they don't rely on concealment.

BACKGROUND MATCHING
--Caprimulgidae: roost in day in exposed places
--open country birds: larks, ptarmigans
--parrots
--grassland birds striped with straw-colored stripes
--Gloger's Rule: animals tend to be dark in humid habitats and light in arid areas.

DISRUPTIVE COLORATION
breast bands, etc., bright colors in jungle, all tend to break up the outline of a bird.

COUNTER SHADING -- makes it look flatter--most birds are dark dorsally and light ventrally.

Functions of color continued. . .

2009-12-07T22:17:00.000-08:00

Black-billed Magpie

2) predator defense via deflection--rump patches, spots in wings or tail. Spots on the tail are especially advantageous because, if they are "caught," damage is limited. Concealed spots may have startle effect.

3) thermoregulation--dark plumage may absorb more radiation than pale ones. Dark makes feathers warm and heat lost more slowly. This may support Gloger's Rule, but it really does not hold water. Light birds are more common in North where the 2 degree advantage in thermoregulation must be outweighed by background matching. Black-billed Magpies face their dark fronts to the sun in the morning and their white sides to the sun in the heat of the afternoon.

4) foraging aides--shorebird eye stripes are "sights" to aim bill with (?). European Kingfishers with covered eyespots inefficient hunters. Fish-eating seabirds ventrally white, so little contrast against the sky (fish see white least well). Most terns are fish-eaters and are white below. Exceptions inlude Black Terns that eat insects, Noddy Terns that are nocturnal and Lava Gulls that are also nocturnal. Spots may startle insects out of hiding and may account for the plumages of mockingbirds and redstarts (look these up in a field guide).

5) mimicry--Basically there are no poisonous birds (although one with toxic feathers and muscles was discovered recently in Borneo--these tasted bad enough that local people don't eat them). Golden-winged Warblers are supposed to mimic chickadees: they often associate together. The advantage for the warbler is that chickadees know area and predators since they are year-round residents. The warbler's black bib lessens interspecific aggression. The advantage for the chickadee is that the warbler can easily open buds that chickadee can then work over. Zone-tailed Hawks and Turkey Vultures converge on flying method and is usually given as an example of aggressive mimicry. Prey is not afraid of the silhouette of a vulture and is surprised when one of the vultures is actually a hawk. Other examples of mimicry usually hypothesize aggressive-dampening effects on competitors.

Lava Gull

Functions of color concluded

2009-12-07T22:12:00.000-08:00

6) Social systems--a catch-all category. The rose on grosbeaks' breasts, why is it there? IT MUST HAVE SOME SOCIAL SIGNIFICANCE! Like species or sex recognition. Color may be for sexual selection for attracting females, as in birds-of-paradise, pheasants, hummingbirds, cotingas, or manakins. Long-distance migrants have short time to breed, so being brightly colored increases role division and efficiency. Role specialization is correlated with dimorphism as is short, intense breeding coupling time.

In Northern Flickers, the male moustache is essential for sex recognition--mates will not recognize each other without it. In Red-winged Blackbirds red shoulders are needed for driving off territorial intruders. In Harris's Sparrows immatures have white throats while adults have black. Adults take optimal feeding sites--bleached adults loose status in the flock. In Mallards' heads and speculums function in sex recognition--dyed males will not find mates. In Yellow Warblers, males are territorial in winter in Central America but will tolerate females in territory. Immature males retain female plumage all winter, thereby deceiving adult males.

One last thought--Convergent Evolution in plumage coloration. This is when two gene pools converge on same strategy for survival. Specific selection (whatever that may be) pressures must be producing same results. African Longclaws and Eastern Meadowlarks look identical. Can you think of other examples?

Adult and Young Harris's Sparrow

Ecology

2009-12-07T18:17:00.000-08:00

Ecology is a whole other course. I will just briefly touch upon several topics of interest. I've skirted "hard" ecology (although some students think I teach ornithology in ecology). In general, bird populations have several characteristics a) numbers are usually stable and fluctuate only within certain limits; b) potential rate of increase is high but seldom realized; and c) number of individuals depends on LIMITING RESOURCES.

MAIN FACTORS AFFECTING POPULATION SIZE are mortality and natality and immigration and emigration (hard to demonstrate). Mortality is studied by means of life tables. Birds are rather unique since the tables show that mortality is not correlated with age -- in other words, no matter what the age of a bird is, it is about equally liable to die.

Controversy exists about how populations are regulated. Is the regulation density dependent or independent? Density dependent factors, especially food, seems to be most important (game management would come in here if one was to cover it).

Black-billed Cuckoo

Geographical Ecology

2009-12-06T23:55:00.000-08:00

ZOOGEOGRAPHY AND BIOGEOGRAPHY EXPLAIN DISTRIBUTION

Present distributions are the result of previous history plus taxonomic history. There are few cosmopolitan species because 1) ecological limits are restricted and 2) barriers to dispersal exist. You might think birds would ignore barriers, but they show regional fidelity despite their flying potential. They are reluctant to cross unsuitable habitat. The best dispersers are in temperate zone.
The HOUSE SPARROW is in Death Valley, having dispersed across the whole country, but the BROWN TOWHEE, also urban, is poor at dispersal--the Farallon Islands, 28 miles from mainland, lack Brown Towhees.

The theory of continental drift revolutionized Zoogeography. There have been many changes through time: i.e., New World Vultures were in the Old World. Mountains have risen; Earth is in a constant state of flux, and we see only a second.... Wegner postulated a single Permian landmass: Pangea. Continental plates move out across the earth's surface (landbridges were used as an explanation for distribution before Continental Drift).

PANTROPICAL DELEMMA
ZOOGEOGRAPHICAL REALMS
ISLAND BIOGEOGRAPHY

House Sparrow

The Pantropical Dilemma

2009-12-06T23:53:00.000-08:00

Blue-headed Parrot

Parrots are PANTROPICAL (they are found all across the tropics): how did they achieve this? Did they evolve before breakup of Pangea? But Pangea broke up way before main radiation of birds! North America was connected only to Asia at time of Archaeopteryx. Most major splitting occurred 65 million years ago (beginning of Cenozoic). 1) So only birds affected are the most primitive ones (or) 2) birds are far older than we think and we haven't found fossils. As far as we know, the major radiation of bird families occurred in the EOCENE, at the same time of the major splitting of the continents. SO WE HAVE THE PANTROPICAL DILEMMA. How do you explain the world wide distributions of parrots, trogons, barbets or sungrebes? Is this an example perfect convergence? Most landbridges are temperate, so did these taxa move across temperate zones? This seems UNLIKELY, since they are strictly tropical groups and the temperate zone would be a severe barrier. I have seen Mangrove Swallows in temperatures in the 40's.

Prehistoric climates and fossil floras suggest tropical floras did exist on these landbridges during EOCENE! (a shifting of poles towards Siberia). It's also possible that there once existed temperate members of the taxa that are now extinct: we need more fossil evidence.

Zoogeographical Realms

2009-12-06T23:51:00.000-08:00

Faunal regions were described 100 years ago by Alfred Wallace. Although these boundaries aren't crisp, they seem to be valid units. Most birds are restricted on one or another realm. See if you can find some of the endemic families in each realm.

Realm	# species	# familes	endemic families
Australian	900	64	13
Oriental	960	66	1
Ethiopian	1550	73	6
Palearctic	1025	69	1
Nearctic	750	62	1
Neotropical	3100	86	31

The Palearctic and Nearctic are the most similar (and are sometimes called the Holarctic). This is because 1) Eocene land bridge is recent; 2) birds here are generalists here and good at dispersal; 3) birds here cold adapted.

The Neotropics are by far the richest: most endemic families. The region has long been isolated creating many opportunities for adaptive radiation. The Andes also present numerous opportunities for isolation. During periods of glaciation, the lowland jungle shrank into isolated islands, also permitting speciation of bird populations. (African lowland forests much more restricted and have provided less opportunity for speciation.)

American Dipper

Trends in bird colonizers:

2009-12-06T23:45:00.000-08:00

(ECOLOGICAL RELEASE)

1) Density compensation--colonizers reach huge numbers without competitors and territories shrink,

2) Increased sexual dimorphism--due to lack of predators colonizers are more able to use resources.
For eample, in the Huia on New Zealand (extinct), the male was straight-billed whereas the female had greatly curved-bill.

3) Longer bills than mainland relatives--bigger prey can be taken now, as well as small stuff.

4) More generalized habitat preferences. Ricklefs and Cox found that the smaller the island, the more generalized the species.

location	number of species	number of habitats occupied/species
Panama	135	2.01
Trinidad	108	2.35
Jamaica	56	3.43
Sta. Lucia	33	4.15

5. There is a trend towards flightlessness. Island birds are also often smaller than mainland populations. All mainland rails fly but many island forms don't. Rhapidae: Dodos. 50 lb. pigeon. All this has to do with lack of mammals and reptiles (only bats, among mammals, are good colonizers).

6. Differentiation--island forms seldom resemble mainland populations. Often you can't tell who they came from because of totally new selective regimes.

7. Adaptive radiation--One island can't produce many new species but this is not so in archipelagos (but can occur on mainland too). Drepanidae (Hawiian Honeycreepers): 28 species from original colonizer now show an incredible diversity of bill shapes. It has been said that if Darwin had visited Hawaii instead of the Galapagos, he would not have come up with his theory of evolution since he would not have deduced the interrelatedness of the birds.

Northern Pintail

MacArthur/Wilson Island Equilibrium Model

2009-12-06T23:43:00.000-08:00

Woodpecker Finch

This model basically states that the number of species on an island is a balance between immigrants and a natural rate of extinction. Increase the rate of immigrants, and the number of species rises. Increase the rate of extinction, and the number falls. You should try to graph this. On your graph, the point where the immigration line and the extinction lines cross, that's your island avifauna.
Island birds are vulnerable to extinction. They must have large populations but they aren't good competitors: they're not specialized. For example, a Woodpecker Finch on the Galapagos makes a passing poor woodpecker, even though that's the "niche" the finch is using. (It collects a small twig to dig out insects from wood.)

Two factors that affect island avifaunas are: 1) distance: the further out an island is, the immigration rate becomes lower so fewer birds. SHOW THIS ON YOUR GRAPH. 2) size: extinction rates are larger on small islands, so small, distant islands will have really small avifaunas. SHOW THIS ON YOUR GRAPH. If this sounds real confusing, try Googling it.

This model has proven hard to prove in field but is useful in its predictive value.

Equilibrium evidence

2009-12-06T23:42:00.000-08:00

Krakatoa, an island near Borneo, exploded in 1883. By 1886 there were no birds to be found; in 1897, still no birds; in 1908 there were 13; in 1920 -- 27, in 1934, 27 again, but 5 were not found from before and there were 5 new ones. So it appears an equilibrium is achieved.

Simberloff studied mangrove islands off Florida. He killed off all insects and found an equilibrium of species numbers attained.

Diamond claimed turnover rates on the Channel Islands off California but he was attacked in print (Lynch and Johnson) who claimed extinction either not so (Diamond just didn't find species) or human-caused, so not natural.

Clearly you need a broad data base to work form. You have to be sure your first birds are really breeders. Also extinction is very hard to prove. Researchers in Peru recently rediscovered the White-winged Guan, a bird thought to be extinct for nearly 100 years, and Ivory-billed Woodpeckers may have been rediscovered in Arkansas.

On the other hand, there is a body of evidence against the equilibrium theory.

Roseate Spoonbill

Data against equilibrium

2009-12-06T23:40:00.000-08:00

Workers in New Zealand saw numbers increasing constantly. Basically the two sides are at an impasse. How about the effects of distance? Diamond found in the New Hebrides that the furthest island have fewest birds, but Abbot and Grant in New Zealand and Australia found no such correlation. David Lack said that even the most remote island has a large number of vagrants, so distance does not really affect island populations (but dispersal is not the same as colonization). Hawaii has very few vagrants (2000 miles from mainland)

How about size? There are many examples that indicate that there is a fairly straight line correlation between size and number of birds, but it may not actually be size that's affecting bird diversity. Size is also correlated with elevation, diversity of base resources, and habitat types available.
David Lack says all this equilibrium stuff is bunk--islands behave just like mainland. But Willis, working on Barro Colorado island (2-3 sq mile island in the middle of the Panama Canal), found that the island looses 10+ species/decade. The only difference is that it is now an island (it wasn't before a dam was erected), when a new equilibrium was presumably created.

Population Ecology

2009-12-06T23:30:00.000-08:00

Two subjects will be discussed here: Competition and Bird Species Diversity

Virginia Rail

Competition

2009-12-06T23:28:00.000-08:00

Interspecific competition is the use of a limited resource by one species that reduces the availability of that resource by other species. In 1925 and 1926, two mathematicians, Lotka and Volterra, predicted that in this situation, one species would reach its carrying capacity at the total exclusion on the other species in that resource. All a species needs is a slight competitive advantage to succeed: the chance of two species' being equal is mathematically tiny. The result is A PARTITIONING OF RESOURCES BY BIRDS. Study after study has confirmed competitive exclusion.

Another interesting aspect of competition is the study of habitat utilization by birds. You should be familiar with the terms niche, habitat, and empty niche. Do you think that the term empty niche is a controdiction in terms? How do the terms possible (fundamental) and actual (realized) niche suit you?

Northern Shrike

Bird Species Diversity

2009-12-06T23:27:00.000-08:00

There are 3 types of diversity: alpha diversity (at single point, restricted area); beta (between point diversity, comparing different alpha diversities); and gamma (broad geographic scale). If point A has 30 species, point B has 30 species and point C has 30 species, and none of these species are shared, then alpha diversity is 30, beta is 60 and gamma is 90. If the points have the same species, then alpha = beta.

Thre are three types of patterns of diversity. You have latitudinal. In Maine you have alpha diversities around 18 (and gamma of 45); Louisiana 30 (150); Mexico 50 (300); Costa Rica 60 (400); Panama 80 (500); Amazon 125 (600). (An interesting exception is that alpha diversities in grasslands remain a fairly constant 5).

Altitudinal (Peru) beta diversity: 500' 200; 5600 144; 6500 128; 8000 106; 9800 66; 11000 25.

Habitat: as you go from grassland to mature forest, you see the following patterns: grassland 5; shrub 10; 2` growth 15; 1` growth 30

The question now arises, HOW DO YOU ADD SPECIES TO A COMMUNITY?

Buff-breasted Sandpiper