10 December 2009

Table of Contents

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).
  • 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

09 December 2009


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


 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 find 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

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.

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?


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?

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.


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

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

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

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

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

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

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.

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

Muscles. Pectoral muscles = 15-40 % of bird's weight (vs. 1-2 % in people—Superman must have been a really strange looking dude). 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

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


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

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

08 December 2009

Archaeopteryx: the first bird

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

 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

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


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


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

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.



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?


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 grebes rather than herons. Sandpipers are close to doves. New World Vultures are close to storks. Warbling Vireos in the Rocky Mountains are probably not the same species as those in the East.

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


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 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

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

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

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?

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

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

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

 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

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

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.


Social Behavior

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

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

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

a) COURTSHIP male chases female
  • 1) SOLITARY by male alone
  • 2) MUTUAL by both sexes
  • 3) COLLECTIVE by 2 or more males together
  • 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

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.


Vocal displays

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


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


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

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

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 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

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?

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

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)

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

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