Why Do North American Vultures Have Either Red Or Black Heads?
A common question posed to ornithology professors, birders and birding guides that has a surprisingly complicated answer
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As a former birding guide, one question that I was often asked was why do turkey vultures have red heads and pale beaks whilst black vultures have black heads and beaks? In the eyes of most casual observers, these two vultures look much alike, except the colors of their heads, which provide a sort of color-coding for quickly distinguishing the two species. Why do they have this obvious color difference? Are there advantages associated with one color versus the other?
From an adaptive point of view, color can serve several functions in animals, and frequently represents a trade-off amongst different evolutionary drivers. These trade-offs can vary between individuals within the same population, and color can even be altered to serve very different purposes, such as thermoregulation and communication.
It is usually assumed that the skin coloration of black vultures, Coragyps atratus, is the result of skin cells containing eumelanins, a group of brown-black pigments in the upper layer of skin (or epidermis) that act as a sunscreen capable of efficiently absorbing UV photons, but how red skin coloration isβ¦
