It’s Sunday, and that means a themed group of birds from biologist John Avise. John’s notes are indented, and you can enlarge the photos, as always, by clicking on them.
In recent weeks, Jerry has posted some of my photos of birds with fancy feathers on their heads (see “Avian Crests, Tufts, and Horns”, and “Other Avian Hair-dos”). Presumably such elaborate head-dressings are attributable to sexual selection. But did you know that some birds have few or no feathers on their heads? Such “bald birds” are the subject of this week’s post. In the case of the carrion-eating vultures, being bald is surely favored by natural selection to help keep the head relatively clean from blood and guts that otherwise would accumulate and mat a bird’s cranial feathers whenever it feeds on a messy carcass.
Condors and storks are related to vultures, so there is probably a phylogenetic component to avian baldness too. Further, newly hatched chicks of various bird species sometimes have few feathers on their heads. Finally, because of its name (which is derived from Old English), I’ve also included the Bald Eagle in this set of photos, despite the fact that its head is covered in white feathers. All of these photographs were taken in Southern California or Florida.
Wood Stork, Mycteria americana:
Wood Stork in flight:
Turkey Vulture, Cathartes aura:
Turkey Vulture in flight:
Turkey Vulture head:
Black Vulture, Corygyps altratus:
Black Vulture in flight:
Black Vulture head:
California Condor, Gymnogyps californianus:
California Condor head:
Wild Turkey, Meleagris gallopavo:
American Coot chick, Fulica americana:
Bald Eagle, Haliaeetus leucocephalus: