A US Customs and Border Protection (CBP) radio tower near the Texas-Mexico border has become home to some 300 vultures, which have coated the structure’s entire surface, both inside and out, as well as the ground below, in “droppings mixed with urine,” according to a request for information the agency issued to vendors this week.
A smoothly-functioning communications network is essential for CBP officers to do their jobs. The agencies under the aegis of the Department of Homeland Security, of which CBP is one, have suffered from radio problems in the past.
The birds in the Texas tower have been roosting there for more than six years, a CBP spokesperson told Quartz, adding, “They will often defecate and vomit from their roost onto buildings below that house employees and equipment. There are anecdotes about birds dropping prey from a height of 300 feet, creating a terrifying and dangerous situation for those concerned.”
As a defense, vultures “regurgitate a reeking and corrosive vomit,” explains a factsheet from the US Department of Agriculture (USDA). This kills bacteria on the birds’ legs, but also eats away at the metal in radio towers, reducing the life of the structure and making it unsafe for the maintenance workers who climb it. Vulture droppings can also carry a range of diseases such as histoplasmosis, salmonella, and encephalitis.
Large groups of vultures smell “like a thousand rotting corpses,” one homeowner told a reporter last August after a vulture colony set up shop at a South Florida country club, forcing the family from their $700,000 vacation home.
The scavenging species feeds mostly on carrion, and undigested fur and bones are commonly found at the base of communications towers within which vultures roost. Black vultures in particular have been known to disembowel and kill young or sick livestock.
“Although black vultures have killed calves up to several days old, they are often attracted by and feed on placentas before damaging a newborn calf or lamb,” according to the USDA’s Animal and Plant Health Inspection Service. “The scent of afterbirth can attract vultures from great distances.”
One solution would be to kill one or more of the vulture flock, which is known as a “kettle.” According to AGL, a trade magazine for cell tower operators, vultures won’t congregate in an area “where one of their own has been injured or killed.”
But the Migratory Bird Treaty Act, which was first enacted in 1918, prohibits the killing of vultures, and violators can be fined up to $200,000 and receive up to a year in federal prison.
Other available solutions include hanging a freeze-dried vulture carcass or “taxidermic effigy” from a tower, which can reduce roosts 93% to 100% within nine days. UV-rated urethane replica carcasses are also commonly used, and don’t decay like dead birds do.
“The intelligently designed and precisely engineered large vulture effigies hang in the head-down position to mimic a struggling or dead black vulture,” according to the AGL.
Fireworks have also been used to scare vultures away from towers, but make a lot of noise. CBP, however, is seeking “minimal” visual and sonic impact to the surrounding area. So the agency is looking for a “viable netting deterrent” to prevent vultures from roosting in its radio towers.
“CBP’s Office of Information Technology has been working closely with several agencies including Fish and Wildlife, the USDA, environmental experts and the Texas State Historical Preservation Officer, to determine a good path toward a solution that will deter the vultures from roosting atop our towers while ensuring no harm to the birds,” the spokesperson said. “Research has shown that netting has proven to be a viable deterrent by restricting the birds from being able to initiate roost.”
There are no nests, or baby birds in the affected tower, according to CBP.
Installation of the netting will begin after the tower is cleaned and repaired, the CBP solicitation says. It expects the nets to be in place by August, “before the natural heavy vulture roosting period during the fall months.”