Cathartidae – New World Vultures

The Cathartidae or New World vultures are the only family of Cathartiformes. The family has seven species in five genera, most of which are monotypic. It includes five vultures and two condors found in warm and temperate areas of the Americas.

The ‘New World’ vultures were widespread in both the Old World and North America during the Neogene. They do not form a monophyletic clade with the superficially similar family of Old-World vultures, but similarities between the two groups are due to convergent evolution. They are closely related to, but distinct from, Accipitriformes – the Old-World vultures and allies.

These vultures are scavenging birds, feeding mostly from carcasses of dead animals without apparent ill effects. Bacteria in the food source, pathogenic to other vertebrates, dominate the vulture’s gut flora, and vultures benefit from the bacterial breakdown of carrion tissue.

California Condor Gymnogyps californianus – ©Dubi Shapiro

New World vultures have a good sense of smell, whereas Old World vultures find carcasses exclusively by sight. A particular characteristic of many vultures is a bald head, devoid of feathers to reduce fouling as they push their head deep into a carcass.

American Black Vulture Coragyps atratus – ©Dubi Shapiro

New World vultures are generally large, ranging in length from the Lesser Yellow-headed Vulture at 56–61 centimetres up to the California Condor and Andean Condor, both of which can reach 120 centimetres in length and weigh 12 or more kilograms. Plumage is predominantly black or brown, and is sometimes marked with white. All species have featherless heads and necks. In some, this skin is brightly coloured, and in the King Vulture it is developed into colourful wattles and outgrowths. They all have long, broad wings and a stiff tail, suitable for soaring and are the best adapted to soaring of all land birds. The feet are clawed but weak and not adapted to grasping. The front toes are long with small webs at their bases. No New World vulture possesses a syrinx, the vocal organ of birds. Therefore, the voice is limited to infrequent grunts and hisses.

Turkey Vulture Cathartes aura – ©Dubi Shapiro

Their beaks are slightly hooked and relatively weak compared with those of other birds of prey. This is because it is adapted to tear the weak flesh of partially rotted carrion, rather than fresh meat. The nostrils are oval and are set in a soft cere. The nasal passage is not divided by a septum (it is perforate), so that when looking from the side, one can see through the beak. The eyes are prominent, and, unlike those of eagles, hawks, and falcons, they are not shaded by a brow bone. Members of Coragyps and Cathartes have a single incomplete row of eyelashes on the upper lid and two rows on the lower lid, while Gymnogyps, Vultur, and Sarcoramphus lack eyelashes altogether.

Andean Condor Vultur gryphus – ©Dubi Shapiro

New World vultures have the unusual habit of urohidrosis, or defecating on their legs to cool them evaporatively. As this behaviour is also present in storks, it is one of the arguments for a close relationship between the two groups.

New World vultures are restricted to the western hemisphere. They can be found from southern Canada to South America. Most species are mainly resident, but the turkey vulture populations breeding in Canada and the northern US migrate south in the northern winter. New World vultures inhabit a large variety of habitats and ecosystems, ranging from deserts to tropical rainforests and at heights of sea level to mountain ranges, using their highly adapted sense of smell to locate carrion. These species of birds are also occasionally seen in human settlements, perhaps emerging to feed upon the food sources provided from roadkill.

New World vultures and condors do not build nests, but lay eggs on bare surfaces. On average one to three eggs are laid, depending on the species. Chicks are naked on hatching and later grow down. Like many birds the parents feed the young by regurgitation. The young are altricial, fledging in 2 to 3 months.