Vulture

About the vulture

Cathartidae includes the New World vultures and condors: seven living species across five genera, found only in the Americas. They are called "New World" vultures to distinguish them from the Old World vultures of Africa, Asia, and Europe — two groups that look and act alike mainly because of convergent evolution rather than a close family relationship. The family includes the black vulture, turkey vulture, lesser and greater yellow-headed vultures, king vulture, California condor, and Andean condor. The family name comes from the Greek word cathartes, meaning "purifier," a nod to the group's scavenging role.

The classification of New World vultures has shifted over time. They were traditionally placed with the falcons and hawks in Falconiformes, and some researchers later argued for a closer relationship to storks based on karyotype, which briefly put them alongside storks and herons in Ciconiiformes. More recent DNA studies instead point to a relationship with the other diurnal birds of prey, and taxonomic authorities now split on whether to fold the family into Accipitriformes or keep it in its own order, Cathartiformes. Within the family, genetic analysis identifies two main groups: one made up of the black vulture together with the three Cathartes species — the lesser and greater yellow-headed vultures and the turkey vulture — and a second made up of the king vulture, the California condor, and the Andean condor.

New World vultures are generally large birds, ranging from the lesser yellow-headed vulture at 56–61 cm (22–24 in) long up to the California and Andean condors, both of which can reach 120 cm (48 in) in length and weigh 12 kg (26 lb) or more. Plumage is mostly black or brown, sometimes marked with white, and every species has a featherless head and neck — in the king vulture, that bare skin develops into colorful wattles and outgrowths. All members of the family have long, broad wings and a stiff tail built for soaring, and they are considered the land birds best adapted to soaring flight. Their feet are clawed but weak, not built for grasping prey, and none of them have a syrinx, the vocal organ most birds use to sing — so their voices are limited to grunts and hisses. The beak is slightly hooked but comparatively weak, suited to tearing softened, partly rotted carrion rather than fresh meat, and the nasal passage runs straight through the beak with no dividing septum. The eyes are prominent and, unlike those of eagles, hawks, and falcons, are not shaded by a bony brow ridge; species in the genera Coragyps and Cathartes carry a single incomplete row of eyelashes on the upper lid and two rows on the lower, while the king vulture and the two condor genera have no eyelashes at all. One unusual shared habit is urohidrosis: New World vultures defecate on their own legs to cool themselves through evaporation, a behavior also seen in storks and cited as one argument for a closer relationship between the two groups.

Behavior and diet

All living New World vultures and condors are scavengers, feeding mainly on carrion along with fruit — especially rotten fruit — and garbage. Species in the genus Cathartes, which includes the turkey vulture, locate carcasses partly by smell, detecting ethyl mercaptan, a gas produced by decaying bodies; their olfactory lobes are unusually large as a result. Other species, such as the American black vulture and the king vulture, have a weak sense of smell and find food mainly by sight, sometimes by following Cathartes vultures to a carcass. Their digestive systems are highly acidic and dominated by anaerobic bacteria that help them tolerate the toxins present in decaying meat; a 2014 study of turkey and black vultures found these same bacteria groups present on the birds' bare facial skin as well as in the gut, likely picked up as the birds push their heads into carcasses to feed.

New World vultures and condors do not build nests; they lay their eggs directly on bare surfaces, typically one to three depending on the species. Chicks hatch naked and grow down feathers afterward, and, as with most birds, parents feed them by regurgitation. Young are altricial, meaning they are helpless at hatching and depend heavily on their parents. Most species fledge in two to three months, but California condor chicks take five to six months and Andean condor chicks six to ten months.

Range and habitat

New World vultures are found only in the Western Hemisphere, ranging from southern Canada down through South America. Most species are largely resident year-round, though the turkey vulture breeds in Canada and the northern United States and migrates south for the winter. As a family, they occupy an unusually wide range of habitats and elevations — deserts, tropical rainforests, and everything from sea level to mountain ranges — and they are sometimes seen around human settlements, drawn in by roadkill and other food sources.

Conservation status

There is no single conservation status for the family as a whole, since the IUCN Red List assesses each species separately and they range from secure to critically threatened. The California condor is Critically Endangered: it once ranged from Baja California to British Columbia but had contracted to California alone by 1937, and in 1987 every surviving individual was brought into a captive breeding program to save the species. As of 2020, the total population stood at 504 birds, with 329 living in the wild and 175 in captivity, according to the Yurok Tribe and the California Condor Recovery Program. The Andean condor is listed as Vulnerable. The American black vulture, turkey vulture, lesser yellow-headed vulture, greater yellow-headed vulture, and king vulture are all listed as Least Concern by the IUCN, though the king vulture's population is showing evidence of decline.