Flexible Soaring Styles Allow Vultures To Stay Aloft Longer and Focused On Dinner

Vultures are not good at flapping their wings, but they manage to spend long periods of time in the air by soaring. In a recent study, scientists explore how these scavenging birds use small-scale turbulence to stay aloft even when weather conditions don't favor the formation of rising air columns.

When observing vultures in flight, Julie Mallon of the University of Maryland and colleagues noticed vultures tend to wobble at low altitudes, but fly in circling patterns high in the air. Researchers call this flexible behavior "contorted soaring" and found it is primarily used when flying less than fifty meters above ground and when the weather was cool and cloudy - conditions not optimal for the development of thermals, which are columns of rising air created by the uneven heating of Earth's surface from solar radiation.

Researchers studied both Turkey Vultures (Cathartes aura) and Black Vultures (Coragyps atratus) at thirteen sites in southeastern Virginia between 2013 and 2014. They took an old-school approach to their study by observing vultures through binoculars and simply recording how long the birds remained in the air and the different methods of flying employed at different altitudes, according to a news release.

Mallon believes vultures make use of small-scale turbulence that forms when horizontal air currents hit the edge of a forest or similar barrier, because it produces a small area of uplift at the tree line and provides the boost these birds need to stay aloft without flapping their wings.

Using this sort of small-scale turbulence along with other sources of updraft appears to increase the amount of time vultures can spend on the wing, searching for food. Researchers found Turkey Vultures particularly benefit from low-altitude contorted soaring because they can easily sniff out dead animals in the forest and avoid competition from higher-flying Black Vultures. (Scroll to read more...)

"Finding vultures to observe was the easiest part of our field work: My field technician and I would sit in camping chairs by the side of the road and wait for the vultures to come to us," Mallon said in the release. "Out of curiosity, locals would often stop and ask us why we were there. After a few weeks, we became quite famous and people would stop just to tell us that they had heard about us!

"We now know soaring flight is more complex than previously thought and merits more study," she added. "Although observational studies are less and less common in the ornithological literature, it is very satisfying that we were able to add this basic knowledge with such a simple approach."

Their findings were recently published in The Auk: Ornithological Advances.

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