|Turkey Vulture (Cathartes aura)|
DESCRIPTION: L=27" (69cm), WS=69" (175cm). Sexes similar. Overall black, with pink head. In flight, wings show dark leading edge and lighter trailing edge and wings are held up in a V pattern (different from most hawks and eagles).
NATURAL HISTORY: Feeds on dead animals (carrion) found by both sight and scent (unusual among birds). Vultures save energy by soaring, using upcurrents of air (thermals) to stay aloft. They also save energy by lowering their body temperature (torpor) at night and then basking while perched (with wings outstretched ) to warm back up in the morning. Their black plumage helps them absorb heat while basking then helps keep them keep cooler (compared to white plumage) while soaring during the hot day looking for carrion (see below). To cool themselves down when too hot, they urinate on their unfeathered, blood vessel-filled legs, allowing for evaporative cooling but staining their legs white.
Having black feathers/fur/exoskeleton helps black animals heat up in the morning and cool off during the day. Here's how it works.
Compared to white, black absorbs more heat, but stops more of the sunlight from penetrating deeper toward the body. When the air is still, during the cold morning hours, the heat absorbed into the black surface has time to conduct inward to the body, heating the animal. During the hotter part of the day, when the animal is flying or running and/or the wind is blowing, the wind (by convection) quickly whisks away the heat that is absorbed by the outer surface before the heat has time to conduct inward to the body. Thus the animal remains cooler than if the sunlight was able to penetrate through white surface into the body.