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