Feb. 22, 2007

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SAN ANTONIO -- In a semi-rural section of northwest San Antonio, dozens of vultures congregate on high-tension electrical towers as if holding a meeting. Others make lazy circles in the air, waiting for an opportunity to land and join them.

"The large black birds we see throughout Texas and refer to as buzzards are actually vultures," said Randy Smith, staff biologist with Texas Wildlife Services in San Antonio. "We have two species of vulture in Texas -- the turkey vulture and the black vulture."

Texas Wildlife Services, part of Texas Cooperative Extension, receives dozens of reports each year about "conflicts" between vultures and humans in Central Texas, Smith said. "Some are isolated or individual instances, while others represent more repetitive or persistent problems," he said.

In this region, vultures have damaged electrical high-tension towers, power lines and buildings, Smith said. They also create a potential hazard to commercial and military aircraft. And vultures in rural areas, especially black vultures, sometimes attack sheep, goats and cows while giving birth, often killing their newborns.

"The black vulture is the one that causes the most damage," Smith said. "Turkey vultures are usually more guilty by association since they're frequently in the company of black vultures."

Black vultures are smaller but more aggressive than turkey vultures, he said. The turkey vulture has a bald red head and neck, while the black vulture has a featherless black head and neck.

While vultures sometimes damage property or injure or kill livestock, they play an important part in the ecosystem, helping speed along disposal of dead animals, Smith said. "Vultures are nature's sanitation crew," he said. "They perform an important service by disposing of carcasses that might possibly cause the spread of disease. But sometimes we need to control them. We do this by non-lethal means whenever possible."

The vulture population in Texas has been steadily growing, Smith said, and this leads to the occasional clash between the vulture and human culture.

"There's been a marked increase in vulture complaints over the past 10 to 15 years," he said. "We know there are more of them than in recent history."

One location where vultures cause damage is electrical high-tension towers, Smith said. The height of these towers and amount of available space where the birds can land and gather make them an attractive roosting place. They also provide a "thermal lift," allowing vultures to take off and soar with minimal effort.

"But the weight of these vultures on the power lines, along with their acidic droppings, can affect electrical lines and their insulators," he said.

"Vultures have been known to short out power lines," Smith said. "And even if they don't cause shorts, they can still cause power spikes or interruptions. For businesses that require a consistent flow of electricity, like a microchip manufacturer, that fluctuation can cause problems and possibly lead to a significant loss of time and money."

Vultures also damage buildings, especially tall ones, he added.

"In addition to the mess made by their droppings, people tend to be disturbed by the presence of vultures outside their office windows," Smith said. "Frequently after they've landed on the ledge of an office building, they will peck at the black rubber stripping around the nearby windows. They peck at this rubber material until the entire seal is removed, compromising the integrity of the window."

Vultures in the vicinity of airports and military air bases create another potential problem, Smith said.

"With vultures within a certain proximity to airfields, there's the possibility of an 'air strike' between them and a plane, especially during takeoff or landing," he said. "And while the chances of vultures actually downing an aircraft are remote, it has happened before."

The greatest potential for damage during vulture/plane contact is what the Federal Aviation Administration calls "engine ingestion" of the bird, Smith said.

"Planes have been downed by much smaller birds than vultures getting sucked into an engine and causing the engine to fail," he said. "And even when the plane lands safely after such a strike, there can still be significant damage to the engine."

Over the past several years in San Antonio, wildlife services has provided vulture control for Southwest Research Institute, City Public Service, owners and managers of various high-rise office and apartment buildings, and restaurant owners.

In the Austin area, wildlife services has done vulture control on electrical high-tension towers, high-rise office buildings and residential areas in the city, said Jacob Hetzel, wildlife damage management biologist for the agency in Austin.

"We've also done control in rural areas of Travis County where there livestock has been attacked," Hetzel said.

Recently the agency helped resolve a vulture problem in New Braunfels.

"Vultures were roosting in trees and other areas in a public park," said Doug Steen, assistant district supervisor for the wildlife agency. "The population had grown and had started to spill over into an adjacent neighborhood. They were roosting in people's trees and on their homes, defecating on their lawns and houses."

Inside the park, vultures were damaging vehicles, including eating wiper blades and vinyl seats, pecking at the caulking in the pool area and defecating on picnic tables.

"We were concerned about the damage and the possible threat to human health in terms of possible disease transmission," Steen said.

After about two weeks of harassment with pyrotechnics, wildlife services was able to drive the vultures out of the neighborhood and reduce their population at the park.

"Some of them are returning to the park, so we'll probably have to go out and harass them again with some more pyrotechnics to get them to move to another location," Steen said.

"We're about the only people who have the expertise and equipment to address problems associated with damage caused by vultures," said Mike Bodenchuck, state director for the organization. "It's appropriate for homeowner associations, utility companies or building owners to contact us in the event they're having a vulture problem. Once we've been contacted, we'll investigate and make an assessment of what we might do to help control the problem."

Depending on the nature and extent of a problem, wildlife services can provide either technical expertise or hands-on assistance, Bodenchuck said.

"In most cases where it's a small problem with a single animal or small number of animals and there's no real threat to human health or safety, we can instruct people what to do to handle the situation themselves," he said. "But if the problem is more serious and persistent, posing a threat to human health or safety, we may have to get directly involved."

In Cental Texas, the agency has provided technical assistance or direct control toward managing racoons, snakes, skunks, coyotes, vultures and other wildlife.

The main form of wildlife control is harassment, Smith added. Other forms of control include trapping and relocating animals or trapping and euthanizing them.

"With vultures, try to drive them from their roosting area with pyrotechnics, especially those with a loud bang or whistle," Smith said. "We also shine laser lights into their faces and eyes to frighten and annoy them. Black birds are especially sensitive to red light." Another means of harassment include firing off propane cannons and hanging vulture "effigies" near roosting areas.

"We also use duck decoys and paint them black to simulate vultures, then hang them off electrical towers or trees," Smith said. "It spooks the vultures because they don't like to see what appears to be one of their own kind dead. It's an effective means of control."

Because vultures, like many other species of bird, are protected under the Migratory Bird Treaty Act, a federal depredation permit is needed to trap or euthanize them, Smith said.

"You don't need a permit from U.S. Fish and Wildlife Services to harass vultures, and so that's usually the first means of controlling the birds," he said. "The next step up is to apply for a permit that allows you to trap and release the birds or trap and kill the birds."

Wildlife services will only euthanize a vulture if that is the only effective means of control, Smith said.

"As with other types of wildlife control, the more tools you have at your disposal, the better the chances for effective results," he said. "But we do whatever we can to preserve vultures or other animals whenever possible. Wildlife plays a vital role in our ecosystem -- and we respect that."