BULL SHOALS, Ark. -- As attempts to deter more than a thousand black vultures from congregating at the Bull Shoals Dam and Powerhouse in the Ozark Mountains of north central Arkansas have failed, the Army Corps of Engineers is trying a new scare tactic.
On Tuesday, officials hung vulture "effigies" in an effort to keep vultures from damaging the dam's structures.
"We'll see if we have a lot of success," said Bruce Caldwell, supervisory natural resource biologist with the corps' Mountain Home Project Office.
An estimated 1,500 to 1,600 vultures have taken up residency at the Bull Shoals Dam and Powerhouse. So far, the birds have caused more than $120,000 in damage to both tower roofs, said Steve Hernandez, the Army Corps of Engineers powerhouse supervisor.
Besides tearing apart the tower roofs, which are a rubbery material, the painted surfaces of the towers are starting to show the effects of the vultures' caustic droppings, he said.
To make matters worse, officials are noticing more vultures are congregating at the Norfork Dam. In mid-January, Caldwell counted about 200 vultures. Last week, he saw an estimated 600 vultures at the dam, he said.
So far, the birds have not caused damage, but it's only a matter of time, Hernandez said.
In late November, officials started using a propane scare cannon at the Bull Shoals Dam and Powerhouse, hoping the three blasts fired every 16 minutes would encourage them to find a different place to roost. Instead, the birds circled around and eventually returned.
"The propane cannon worked for about a month," Caldwell said.
Their hope was the cannon would work until cold weather hit, but the area didn't experience a bad enough winter for the birds to leave.
"We still use it, but they sit and look at it now," Hernandez said. "It appears all deterrents work for a short duration. There doesn't seem to be a good answer, a long-term solution, for this problem."
Besides the scare cannon, officials have tried other nonlethal methods, such as spike strips on the towers and a bird repellent gel on railings. And now effigies.
The good news is that others have had success using vulture effigies.
Although vultures eat dead animals, they do not like to be around dead of its own kind, said Caldwell, citing a 2009 study by wildlife specialist Steven A. Ball with the U.S. Department of Agriculture, Animal and Plant Health Inspection Services, Wildlife Services.
The 10 effigies were made from corrugated plastic with a 3-D element to their "bodies." They will be hung upside down, which appears unnatural to the birds.
Vultures are federally protected under the Migratory Bird Treaty Act. A special permit to shoot them can be obtained through the U.S. Fish and Wildlife Service if it can be proven they are damaging property, Caldwell said.
But, local officials say shooting the birds is a last resort.
"We don't have plans to shoot them right now," Caldwell said. "We're hoping these other things will work, or will buy us time until we get a more severe winter next year."
As for the damaged structures, Hernandez said they will patch the tower roofs at the Bull Shoals Dam until they get funding to replace them with a polyvinyl chloride material. That material is used on the roofs of the Bull Shoals Powerhouse and the towers at Norfork Dam, and the vultures are leaving it alone.
In the meantime, officials are hoping the vulture effigies will make the birds leave. However, they realize the areas above the dams are ideal environments for the bird of prey.
The vultures like the high perches, the warm updrafts and the good food supply of dead fish the areas offer.
"If you're a vulture, what else do you live for?" Caldwell said.