Geography of Vultures in the United States
The United States is home to three species of vultures: turkey vulture, black vulture, and the California condor.
What are vultures?
Vultures are in a category of scavenging birds of prey (or raptors) that feed exclusively on carrion. This means that vultures only feed on the decaying carcasses of dead animals.
Vultures in the United States are a critical part of the ecosystem and clean up carrion, which helps control disease spread. Vultures are also essential for nutrient recycling, returning nutrients from carcasses back into the ecosystem.
Vultures in the United States all belong to the New World vulture or condor family. New World vultures evolved separately from Old World vultures and are adapted to the warm climates of the Americas.
The term “Cathartidae,” representing the family of New World vultures, originates from a Greek word that translates to “purifier.”
There are seven New World vulture species. Three are found in the United States: the turkey vulture, black vulture, and the California condor. The other four species are the Lesser Yellow-headed Vulture, Greater Yellow-headed Vulture, King Vulture, and the Andean Condor.
New World vultures have a bare head and often bare neck, thought to be adaptations for hygiene, enabling the birds to stay clean after feeding on rotting meat.
While vultures in the United States look similar to vultures found in Europe, Asia, and Africa, they are not related. Known as convergent evolution, these unrelated groups of vultures evolved similar features.
In the United States, vultures are known colloquially as “buzzards” although this term is technically not correct as the word refers to several species of hawks of the Genus Buteo that populate Europe.
A group of vultures in flight is known as a ‘kettle’. A group of vultures clustered on the ground or in trees is called a ‘committee’.
Unlike most raptors which rely on their eyesight or hearing to hunt for food, vultures have a heightened sense of smell. This lets them smell carrion up to a mile away.
Turkey Vultures (Cathartes aura) are named for their red, featherless heads that bear resemblance to wild turkeys. Turkey vultures have a six-foot wingspan and weigh between 3.5 to 5 pounds.
The turkey vulture is the most common vulture found in the United States. Turkey vulture can be found during the summer mating season across most of the continental United States and are found all year long in the lower areas.
They cover a broad geographic range that spans from Southern Canada to the southernmost tip of South America. These vultures are seasonal migrators in the northern parts of their range, retreating to the south in the winter, but they are year-round residents in the southern United States, Central America, and South America.
Turkey Vultures are famous for their extraordinary sense of smell, which they use to locate their primary food source: carrion. This remarkable adaptation allows them to occupy diverse habitats, including forests, deserts, grasslands, and suburban areas.
Turkey Vultures have the largest olfactory system of all birds, making them unique among avian scavengers, most of which have a relatively weak sense of smell.
Specifically, Turkey Vultures can detect the scent of ethyl mercaptan, a gas produced by decaying animals, even in minute quantities. This incredible olfactory ability allows them to find carrion hidden under a forest canopy or otherwise out of sight.
It’s not uncommon to observe Turkey Vultures following a zigzag flight pattern low to the ground as they follow the scent of a potential meal.
Black vultures (Coragyps atratus) are easily identified by their black plumage, short tails, and broad wings. They predominantly inhabit the southeastern states, extending into Texas, and their range has been gradually expanding northward.
Unlike their close relatives, the Turkey Vultures, Black Vultures are more social and opportunistic, often scavenging in large groups.
The black vulture’s range expansion has been linked to changes in land use, increased food availability, and warming winter temperatures due to climate change.
Black Vultures, on the other hand, primarily rely on their exceptional vision to find food. They often fly at high altitudes, scanning the ground for carcasses.
In addition, Black Vultures are known to watch for Turkey Vultures starting to descend, indicating the presence of a carcass. Because of their more aggressive nature, Black Vultures will often displace Turkey Vultures once the food source has been located.
Vultures also use communal roosts and soaring flights as ways to find food. By gathering together at night and taking off together in the morning, vultures increase their chances of finding carrion.
If one vulture finds food, it may draw others down to the meal, creating feeding aggregations. This social behavior increases the likelihood that even a solitary vulture can find a meal by following its peers.
California condor (Gymnogyps californianus) is a critically endangered species and the largest land bird in North America. The condor represents arguably the most captivating vulture species in the US.
The California condor is native to the Pacific coast, particularly California and Arizona, with a smaller population reintroduced in Baja California, Mexico. The condor is a gigantic bird, with a wingspan up to 9.5 feet, once soared across much of North America, but habitat loss, lead poisoning, and other human activities nearly caused its extinction.
Through considerable conservation efforts, including captive breeding and reintroduction programs, California condor numbers have slowly been increasing. However, they are still mainly restricted to the Grand Canyon area, the coastal mountains of southern and central California, and northern Baja California.
Geography affects the distribution of vultures in the United States
Multiple factors impact the geographical distribution of these vulture species, including food availability, climate, and human activities.
Food availability is central to the geographic range of vultures. Black and Turkey Vultures are scavengers, feeding mostly on dead animals. Their presence, therefore, is most prominent in areas with abundant wildlife or where human activities provide carrion.
Climate and weather also play a crucial role in vulture geography. For example, Turkey Vultures are partial migrators, shifting southward to avoid the harsh winters in the northern parts of their range. Moreover, the expansion of Black Vultures has been partly attributed to warmer winters in the northeastern US due to climate change.
Lastly, human activities significantly impact vulture distribution. Habitat loss, hunting, and poisoning have restricted the range of species like the California Condor. Conversely, changes in agricultural practices and roadkill have increased food availability and roosting conditions, expanding the range for Black and Turkey Vultures.
Avery, M. L. (2004). Trends in North American vulture populations. In Proceedings of the Vertebrate Pest Conference (Vol. 21, No. 21). https://escholarship.org/uc/item/66q02691
Hill, J. E., Kellner, K. F., Kluever, B. M., Avery, M. L., Humphrey, J. S., Tillman, E. A., … & Belant, J. L. (2021). Landscape transformations produce favorable roosting conditions for turkey vultures and black vultures. Scientific Reports, 11(1), 14793. https://doi.org/10.1038/s41598-021-94045-3