An immature turkey vulture (Cathartes aura) stretches before take-off, soon following dozens of its conspecifics to roost together for the night. Black vultures and turkey vultures overlap in distribution and can often be seen together. Generally, it is thought that turkey vultures avoid high black vulture densities, possibly because the latter are more audacious in their interactions. In Missouri, black vultures have been extending their range northward, migrating further during warmer winters. Black vultures differ from turkey vultures in that they are also willing to take live prey. As groups, they are known to harass more vulnerable animals, especially young calves, which poses an issue for livestock owners. In Kenya, similar issues exist with the hooded vulture (Necrosyrtes monachus), and white-backed vultures (Gyps africanus), among numerous other vulture species. Due to poisoning of carcasses, many Old World vultures have become critically endangered in the last decade with populations declines greater than 80–90%. Once common residents, vultures are much more rarely seen in many regions.
But, back to the North American vultures. For the longest time, when I looked to the sky to see vultures with black heads, I had assumed they were black vultures, but that is not the case. Turkey vultures can be differentiated from black vultures (Coragyps atratus) in several ways. Most notably, turkey vultures develop a bright red head when they mature. In juveniles, they lack this coloration entirely. In flight, the ventral side of the wings are mostly black with white tips in black vultures, while in turkey vultures the white color slopes inward to touch the abdomen. When perched, the shape of the head is a dead giveaway. Black vultures have longer and more slender beaks and a bumpy head, contrasting with turkey vultures which have wider skulls and enlarged nasal cavities.
Both vultures photographed in situ