Vultures are considered to be obligate soaring birds, meaning that they use thermal updrafts and orographic lift to assist them in-flight. A thermal updraft is warm air that rises up into the atmosphere. Orographic lift is also a kind of updraft. This type of updraft, or lift, occurs as as air moves from a low elevation over an incline, like a mountain.
Updrafts and lifts are essential for vultures because it helps them to conserve energy. Much like going downhill on your bicycle, why pedal when you can cruise? It’s the same with vultures, why flap when you can soar? However, it’s not always smooth cruising on the thermals for vultures. Sometimes birds experience in-flight turbulence which causes them to deviate from their initial flight path. This type of flight is known as “contorted soaring”.
According to a study published by The Auk Ornithological Advances, in-flight turbulence is good for soaring birds. One-hundred seven black vultures (Coragyps atratus) and 464 turkey vultures (Cathartes aura) were observed for the study which took place in Virginia. Previous studies have shown that vultures use thermal updrafts and orographic lift to assist with soaring. This study showed that the in-flight turbulence that causes contorted soaring also assists vultures. Both species of birds used contorted soaring to assist them when weather conditions are unfavorable for the other types of soaring.
Turkey vultures use their sense of smell to locate carrion, but black vultures do not and they sometimes rely on turkey vultures to locate their meals.
Turkey vultures seemed to benefit more from in-flight turbulence because it allowed them to stay airborne for longer periods of time and at lower altitudes than black vultures. Turkey vultures use their sense of smell to locate carrion, but black vultures do not and they sometimes rely on turkey vultures to locate their meals. The turkey vulture’s ability to stay in-flight at lower altitudes than black vultures coupled with their use of olfaction to locate carrion means that in-flight turbulence might give turkey vultures an advantage over black vultures when it comes to food competition.
The researchers hope that understanding the use of contorted soaring in turkey and black vultures will help them to understand the impacts of in-flight turbulence in other birds such as lesser yellow-headed vultures (Carthartes burrovianus).