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Black vultures. By John James APP. |
What birds do you associate with Halloween? Ravens, perhaps, or crows? Don’t forget vultures. What could be creepier than a bald bird that feeds on rotting flesh?
Seven vulture species populate the Americas. Of those, U.S. residents are most likely to spot two: the black vulture and the turkey vulture (the latter is the most widely distributed species in North and South America). So what makes them different? APP contributing editor T. Edward Nickens explains:
To quickly discern them in flight, watch for a wobbling, or tilting motion unique to turkey vultures. Black vultures are too heavy to wobble; they just glide on wings held flat.
Black vultures also lack the strong V-shape dihedral wing outline of turkey vultures, and they punctuate soaring glides with strong wing flaps. Their motion is hurried, as if they have to work at staying aloft. In contrast, turkey vultures have slower, deeper wing beats, and they flap less frequently. From below, it’s easy to distinguish the short, blunt tails of black vultures from the rudderlike tails of turkey vultures. Black vultures’ underwings sport a silvery white patch at the ends, whereas turkey vultures display a broad, gray, trailing edge along the length of each wing. Sitting, a black vulture’s gray head and longer bill are quite different from its cousin’s blunter bill and hamburger-red head. And getting close is sometimes no problem at all.
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Turkey vultures. By John James APP. |
The olfactory bulbs of black vultures are much less developed than those of turkey vultures, too. Indeed, while turkey vultures rely heavily on smell to locate prey, black vultures are more visually oriented. They tend to fly higher than turkey vultures, spot other vultures circling over carrion, then soar in for the steal. And even though black vultures are slightly smaller than turkey vultures, they gather in large groups and will quickly drive turkey vultures off a prize find of carrion.
Although both species tend to roost in large numbers—roosts can commonly contain more than 1,000 birds—black vultures “are infinitely more social than turkey vultures,” explains Keith Bildstein, director of conservation science for Pennsylvania’s Hawk Mountain Sanctuary. Turkey vultures tend to forage alone, while black vultures feed in groups. In fact, DNA testing of black vultures in communal roosts showed that roosts are comprised largely of nuclear families and their kin. While black vultures bond for life, they may not breed until their more mature years. In a marked population followed for 13 years, for example, the earliest age of first breeding for a black vulture was when a bird was eight years old. Once they’re parents, black vultures shepherd the kids for a relatively long period of time. Adult birds feed young for as long as eight months after they fledge, reinforcing kinship bonds. The family that preys together, so it seems, stays together.