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Management Methods

What can be done to help vultures and humans coexist more easily? In outlying areas, woodlands, farmlands and the like, and at industrial facilities, pyrotechnics such as screamers and cracker shells, have been used to move the birds, but few biologists see the use of that technique alone as an answer to the problem. The birds easily become used to the sounds and are soon no longer bothered by them.

One intriguing new method of vulture dispersal may be the placement of an effigy or mount of a dead vulture in areas where the birds congregate.

"Quite some time ago, we shot a vulture that we couldn't retrieve in a roost, and we noticed quite clearly that the other vultures left the roost," said Thomas Seamans, USDA/Wildlife Services/National Wildlife Research Center biologist.

Seamans had also talked with Edward Davis at the Vertebrate Pest Conference in 1998. Davis, in his work in Texas, mentioned that he had shot some birds he couldn't retrieve and he also had noticed that the other vultures tended to stay away from the area containing the carcasses.

"Taking those 2 bits of information, together with the general consensus among biologists that, on occasion, a dead bird of the same species seems to have a repellent effect on others of the same species, we decided to see if a dead vulture would have an effect on other vultures," Seamans continued.

Through Davis, Seamans obtained a vulture carcass and had a taxidermic mount prepared by the Smithsonian Institution. In a 1999 trial, the vulture effigy was placed in a rocket tower used by NASA near Sandusky, Ohio. The tower was over 200 feet high and had I-beam walkways. After biologists established how many birds used the tower daily, the effigy was introduced.

"First, we laid the effigy flat on a walkway," Seamans said. "Within 3 days the vultures were sitting on the effigy, pecking at it. So that didn't work." They next hung the bird, head down, so it could sway in the breeze. The vultures stayed away.

Unfortunately, the 1999 study was done as the migration season was starting so researchers were unsure if it was the effigy or migration that kept the vultures away. In a re-test done this year, Seamans and colleagues were able to document a significant change in bird numbers before and after hanging the effigy. "We watched the walkway for 1 week, then hung the effigy up for 7 weeks, took it down and watched the tower for another 4 weeks," Seamans reported. "After the third week, there wasn't another vulture on the tower."

After the effigy was used in trials in Ohio with turkey vultures, Michael L. Avery (National Wildlife Research Center - Florida) decided to try the same thing in Florida with black vultures. In three instances, scientists installed either recently killed birds, older carcasses or a taxidermic mount of vultures in communication towers, each 200 to 300 feet high. The birds stopped roosting on the towers.

Avery recalled 1 of the tests in which they installed a carcass. Vultures vacated not only the tower but the whole area. "This tower had about 150 to 200 birds on it," Avery said. "The birds not only roosted on the tower, but they'd fly a mile or 2 to a pig farm and spend the day cavorting with the pigs, eating pig food and pig poop. The farmer there had complained that he couldn't raise piglets because the vultures would kill them. Well, those vultures are not only not on the tower anymore, but they're not at the pig farm. We're getting the impression that this carcass has an impact not only on the immediate roost but for a certain radius around it. It could be a very effective tool."

Another possible new vulture management tool under study by National Wildlife Research Center scientists is the laser. When roosts are in residential areas, using fireworks and other pyrotechnics to move birds is not feasible because of the noise. Shooting is restricted in these areas. In Florida, Avery and other biologists have done preliminary trials using moving laser beams to disperse vultures from large roosts. Lasers can be used from a distance and are quiet. The handheld laser device is like a big flashlight. The laser is used after dark when its red beam is visible to the birds. The beam is projected wherever the birds are and can moved in whatever pattern is wanted or needed.

"It does take some persistence to get the birds to leave the trees," Avery noted. "You keep moving them and keep moving them and eventually they'll get up and leave. The trick is to keep them from coming back the next day, so it would be a matter of persisting night after night after night for however long it takes before you can discourage them from even trying to come back. One night's not going to do it."

Another tool for dispersing vultures that scientists have yet to research is habitat modification. "There should be certain characteristics of the vegetation that these birds are liking," Avery said. "If you thinned out the trees or pruned them or something to alter the structure of the habitat, that may make it less attractive to birds. This type of roost management has been done with blackbirds but no one has done it with vultures."

Most nonlethal bird management techniques, like the ones listed above, will not provide a lasting solution to problems when used alone. Birds become accustomed to noises, light and whatever else is used and eventually are no longer frightened by them. As always, biologists advocate use of a combination of dispersal techniques for effective management.

At the present time, the only established long-lasting solution to vulture problems is to shoot them and shooting is not allowed under federal law without first obtaining a permit from the U.S. Fish and Wildlife Service. The permit application process is time-consuming and the permit short-lived. Besides, as Martin Lowney (USDA/Wildlife Services biologist) notes, "I'm hesitant to use that. Population dynamics of vultures are poorly understood and so poorly documented that I'd have biological concerns about what I'm doing."

"Our goal is not to reduce the numbers of the bird," Seamans agreed. "Vultures play an important role in the ecology of the area. However, in the wrong spot, they become a nuisance. If we can move vultures from the neighborhood roosts around people's houses to a vacant wood lot not near houses, that's fine. We've still got the birds, they're doing what they're supposed to be doing and they're not bothering anybody."

"They're a neat bird," Seamans summed up, "but they are disgusting."