The Life of Birds

adaptation Adelie Penguins adult Africa air sacs altricial America American Robin animal avian barbules beak behavior bird song bird's blood bones breeding season brood calls cells cent Chaffinch chicken chicks clutch colony color Corvus courtship cycle diet Domestic ducklings ducks eagles eggs European European Robin example eyes feathers feeding female FIGURE finches fixed action patterns flight flock flycatchers function glands Grouse gulls habitat hatching hawks heat hormones House Sparrow House Wren hummingbirds imprinting incubation insects instinctive Larus layer legs living male mammals mate metabolic meters molt muscles nest normal oviduct owls pair parasites parents passerines patterns peck penguins pigeons pigment plumage population predators probably regions reproductive Robin sexual singing Song Sparrow species species of birds Starlings stimulate swallows temperature terns territory tion trachea tropical Turdus vertebrates Warbler wing winter woodpeckers Wren young birds