We have three native vultures in North America, tho the Condor is on its last legs.
The turkey vultures (several related species in the tropics) are an anomaly, they can find carrion by scent. Compared to other vultures they can efficiently forage low enough to locate food by odor, a trait especially useful in forested areas. To aid this low altitude foraging technique they have an extremely low wing-loading, allowing then to soar at lower altitudes and in cooler weather.
Black vultures are heavier and aerodynamically speaking, more resemble Old World vultures in flight profile. Like them, black vultures are designed to cruise efficiently (about 45 mph) all day long on high altitude thermals.
Black vultures live in permanent clans where the members are related
From their high vantage point, black vultures observe each other across the sky and also observe turkey vultures. When a turkey vulture finds a hidden carcass, black vultures will follow it down. Surrounding vultures see another black vulture descending and converge on that spot. This is why you might see 10 black vultures and just 2 turkey vultures on a carcass. Black vultures, being heavier, can also displace turkey vultures from a carcass.
The really interesting thing is that at the communal roost site, a black vulture that has found carrion can communicate that knowledge to their clan members, the whole clan following that one bird in the morning.
The edge turkey vultures have is that they can get up in the air earlier in the morning and in less-clement weather, and are also found further north than black vultures.
Old World vultures are close kin to hawks and eagles and it shows.
IIRC New World vultures are actually related to storks.
