This Turkey Vulture was taking an extra long time to preen, maybe it just finished a big meal and was cleaning up after. Having a relatively featherless head is helpful when you make your living plunging it into rotting carcasses. They are known to excrete waste directly onto their legs, staining them white, which can help with thermoregulation and the uric acid is highly acidic which helps to kill off harmful bacteria picked up while feeding. (Click image for larger versions)
