Bird Coloration starts off boldly. Across from a stunning full-page photograph of a handsome bird with a cape of iridescent multicolored hackles, the caption announces, “There are no orange, green, or blue pigments in the feathers of this Nicobar pigeon.” Hill announces the book’s aims: to tell us the whats and whys of bird coloration, and “to communicate in prose accessible to non-scientists what scientists know about the coloration of birds.” (Much later, he raises the possibility that color may have “no function at all,” though he more or less manages to shoot that one down.)
The well-illustrated book marches briskly through the diverse aspects of bird coloration; of variation, the stuff of birding; of differences between the sexes; of molts, ages, subspecies; of what birds see; of measuring and describing color; of pigments and structural colors (you can wash the first out with chemicals or even water, but to destroy the second you must “hit it with a hammer” as a grad student correctly answers); of genetics and environment, feather wear, camouflage, and more.
His examples are as vivid as the illustrations, and in some instances work with them. An ultraviolet photograph of a Blue Whistling Thrush, a brilliant species I once saw in Asia, shows a unique pattern of spots invisible to the human eye. The brilliant yellow face on an Egyptian Vulture is attributed to the nutrients it gets from the guts of dead sheep. A dying albino frigatebird with abraded plumage illustrates why many birds have black wingtips. One of Abbott Thayer’s beautiful but deranged oils, purporting to show that a Blue Jay’s plumage evolved to camouflage it against blue-tinted snow in the winter, is almost vindicated by a potoo that looks more like a broken limb than a bird. He visits the improbable three-morph male “signaling system” of the Ruff, and explains more of its subtleties.
After a quick look at evolution (carotenoid pigment evolved after the dinosaur era Ratites and “Galloanserae”) and an intriguing “unifying concept” (small birds tend to be counter-shaded, medium spotted, or barred, and large ones have large patches of bold colors) he circles back to “why?” And answers, wisely, that we still don’t know.