Vultures prefer to roost near civilization

Human-modified landscapes help birds fly and provide better access to food

Man-made landscapes often make it difficult for wildlife unless you are a vulture, according to a new study by researchers at the University of Georgia.

Since the late 1960s, researchers have noted a steady increase in populations of black vultures and turkey vulture in most of their North and South American ranges. While conservation legislation has certainly played a role, the increase is also attributed to better resting conditions resulting from man-made landscapes, according to Jacob Hill, postdoctoral research associate at UGA’s Savannah River Ecology Lab. .

The combination of managed land and open areas like wetlands, forests and dirt roads works to the benefit of birds by producing obstructive air currents that are reflected from one type of structure to another. , creating an updraft that helps them fly, Hill said, adding that the roads have a similar effect.

Evaluating GPS satellite tracking data from a study conducted by the United States Department of Agriculture, Hill and his research team compared where the birds used to roost to see if they were resting in natural habitats or near areas modified by man. Published in the journal Scientific Reports, the results have consistently shown that birds select perch locations near roads and in fragmented landscapes.

Vultures perch on a communications tower in Beaufort, South Carolina. (Photo submitted)

“Birds have a great deal of flexibility in where they can roost, but certain conditions, such as a moderate amount of landscape change, are going to work for them.” Hill said.

Vultures appear to do just as well in human-modified landscapes as they do in natural landscapes, and often better, said Travis DeVault, study co-author and associate director of SREL.

“Because they are very large birds, they cannot take off as easily as small birds. They depend on the warming of the earth’s surface to produce thermal current. They can use the currents around them to lift them up, ”he said. “Landscape changes like roads paved with asphalt and concrete produce these thermal currents.”

Although the roads pose a risk, Hill said the benefits of a roadside meal outweigh the risks, and the birds seem to know when to take that risk.

“These vultures were found near the intermediate roads. The intermediate levels of the roads are probably what you would find in a small suburb or town, ”he said. “Somewhere between an agricultural area with few roads and a big city with a high density of roads.

A black vulture on the ground investigates a carcass site in a pine forest.

A black vulture investigates a carcass site in a pine forest. (Photo submitted)

The USDA study the researchers analyzed followed seven turkey vultures and 11 black vultures for nearly 8,000 nights at a military base in Beaufort, South Carolina.

Night roosts were determined by isolating the vultures’ last location before sunset and their first location before sunrise. If the location was the same, the place was identified as the night lodge.

The research team’s results were slightly more consistent for vultures.

Distinguished from their black-headed cousins ​​by their red heads and sometimes dark brown feathers instead of black, turkey vultures can sniff out a hidden carcass.

“Turkish vultures tend to be a bit more influenced by the landscape. As more social beings, black vultures are more influenced by where other black vultures are, and as a result, they often reuse perches, ”Hill said.

Researchers report that vultures frequently roost near shopping malls in urban areas where they take advantage of fine dining options in the form of discarded trash. However, this was not the case with these vultures. They perched in areas with less human development, potentially to avoid encounters with people.

DeVault said these birds show flexibility in both their diet and their home range (how much they move around the landscape). Their food sources can vary from pets to road victims and depend on where they live and the resources available.

The researchers said it was essential to study these birds to develop appropriate management techniques because of the incredible paradox they present.

“While vultures provide a huge benefit to the ecosystem by removing dead carcasses from the landscape, thereby reducing the spread of disease, a balance is needed to deal with the potential risks of aircraft collisions,” DeVault said.

Additional study co-authors are Kenneth F. Kellner and Jerrold L. Belant, Global Wildlife Conservation Center, State University of New York College of Environmental Science and Forestry, Syracuse, New York, 13210; Bryan M. Kluever, Michael L. Avery, John S. Humphrey and Eric A. Tillman, United States Department of Agriculture, Wildlife Services, National Wildlife Research Center, Florida Field Station, Gainesville, Florida, 32641.

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