Field Guide: Know Your Turkey (Vulture)
by Kaleigh Hoynes, Fall 2022 Intern
Vultures are generally thought of as icky, ugly, bald-headed birds that you can see feasting on dead things on the side of the road. In popular media, vultures are portrayed as harbingers of death and serve as sinister omens. However, vultures are integral parts of the ecosystem and deserve a little more credit.
Here in the southeastern United States, we only see the turkey vulture (Cathartes aura) and black vulture (Coragyps artratus). Turkey vultures get their name from the fact that their heads are red and featherless, just like a turkey’s head. However, the reason for each species to have evolved a bald, brightly colored head is very different from each other.
Wild turkeys’ heads have a bald head to attract mates and as a way to cool off since the red coloration is due to the concentration of blood veins that are extremely close to the surface of the skin. Turkey vultures on the other hand evolved to have a bald head as an effect of their niche (or role in the habitat). Black vultures get their name from their all-black heads. Vultures are scavengers which means they primarily eat carrion, or dead animals. Almost all vulture species are bald as to not have any pieces of carrion get stuck on head feathers while they’re feeding.
Turkey vultures also have some other interesting adaptations for eating carrion. Turkey vultures have the largest olfactory (smell) system of all birds. The olfactory bulb in a turkey vulture’s brain is 4 times larger than black vultures and they also have twice as many mitral cells (cells that aid in transmitting smell information to the brain) in their brains compared to black vultures. If you look at their nostrils, you will notice that they are extremely large. This is to aid in smelling the cocktail of gas chemicals that are emitted from carrion and then locating the carrion.
Since turkey vultures rely on smell for finding their next food source, they often fly low to the ground. Black vultures, on the other hand, will fly at higher altitudes and use their eyesight to find carrion. Since black vultures usually fly above turkey vultures, black vultures often use turkey vultures to find carrion by looking for turkey vultures who have already found carrion. Turkey vulture’s feet are also very interesting. They do not look like the feet and talons of any other raptor species; they more closely resemble chicken feet. This is to help turkey vultures tear apart carrion. Their beaks are also extremely powerful and sharp to also aid in tearing apart carrion.
Vultures are described as obligate scavengers, which means they rely almost entirely on carrion as a food source. As a result, vultures and other scavengers fill necessary ecological roles within the environment and facilitate nutrient distribution, altered disease dynamics, linkage of food webs, and removal of carrion from the environment. For example, in the absence of vultures, carrion resides in the landscape longer, allowing time for more mammal scavengers to visit and consume carrion which could increase the transfer of disease between mammals and, subsequently, humans.
However, vulture species are currently facing numerous extinction threats, with 72% of vulture species globally experiencing population declines and over half considered endangered or critically endangered. The decline in vulture populations is largely due to human activities and the bioaccumulation of anthropogenic contaminants introduced into the environment. Indeed, 95% of reported deaths in threatened or near-threatened vulture species have been linked to dietary toxins. For example, the drastic decrease in vulture populations in India has been attributed to the use of the veterinary drug dicoflenac to treat livestock. Similarly, vulture populations in Africa have declined due to both intentional killings (poachers poisoning left-over kills to avoid the attention generated by circling vultures), unintentional killings (feeding on carcasses poisoned by farmers to kill livestock predators), traditional medicine, and other anthropogenic causes.
Luckily, turkey vulture and black vulture populations are increasing and there do not seem to be any threats currently facing either species here in the southeast. This is due in part to the fact that both species are protected under the Migratory Bird Treaty Act of 1918. Both species have also expressed an increased tolerance of dietary toxins and do not succumb to higher loads of toxin than other vulture species. However, research in dietary toxins and their effects on both species has not been studied fully and could still threaten either species in the future. Vultures are an integral part of the ecosystem, and their absence would be detrimental. As we approach the holidays, I hope you remember turkey vultures and give thanks to them for being nature’s garbage men and keeping our landscape clean.
