Disease impacting big birds that feed on carrion
By Mike Lynch
Bald eagles are testing positive for a highly contagious form of avian flu more frequently than any other bird in New York state, records show.
A database maintained by the U.S. Department of Agriculture shows that 19 bald eagles have tested positive, including several in the Adirondacks. All the eagles and other birds on the USDA’s list have died.
That includes six eagles from Clinton, Franklin, Jefferson, Washington and Saratoga counties.
The problem could also be compounded because the infections occurred during the breeding season and the virus can be passed from adults to their young.
There are 170 nesting pairs of bald eagles in New York state, according to the state Department of Environmental Conservation’s website.
Lead poisoning also a problem
Krysten Schuler is a wildlife disease ecologist with the College of Veterinary Medicine at Cornell University, which does contract work for the state’s wildlife health program. As part of her work, Schulter has been testing birds for the virus.
Schuler said that Cornell is studying a possible link with lead poisoning.
Lead exposure isn’t necessarily killing eagles, but it makes them less able to fight off infectious diseases or deal with other threats.
“They’re sort of stretched to the max,” she said. “Their checkbooks are sort of maxed out. They’re still in the black but they could get pushed into the red.”
One way eagles get lead in their system is by eating carcasses of deer after the animals have been killed by hunters using lead bullets and left in the wild.
“Eagles see that as a free meal, then those tiny fragments of lead are readily absorbed through their digestive juices into their body, and their eagles are especially susceptible to lead,” Schuler said.
Schuler said foraging appears to determine which birds become infected. She noted that osprey, which feed on fish, aren’t getting the disease. However, raptors such as eagles, turkey vultures, hawks and owls apparently are picking it up. These species eat a variety of terrestrial mammals, including birds.
“The reason so many birds are being affected, like vultures and red-tailed hawks, is that they are likely scavenging other dead birds and getting infected that way,” Schuler said.
Cases in other birds
Eleven turkey vultures have tested positive, including three in St. Lawrence County and one in Warren County, according to the USDA. In addition, five great horned owls, two in Albany County and three in Long Island, have tested positive. Plus, seven red-tailed hawks are known to be infected, although none have been found in the Adirondack region.
Overall, avian flu has been tied to sickness among a wide variety of birds, including chickens and waterfowl. In New York, five Canada geese are known to have been infected, including two in Clinton County. Four snow geese, all in the Finger Lakes region, have tested positive.
Asked about the potential impact of avian flu on the eagle population, a DEC spokesman said “for most species, DEC does not anticipate a population impact related to HPAI (highly pathogenic avian influenza). However, it seems that bald eagles are succumbing to infection in significant numbers both in New York State and in some other states, so it is possible that HPAI may have an impact on eagle populations.”
DEC did note that the state’s eagle population has been increasing significantly since the 1970s. They are currently listed as a threatened species in New York.
DEC announced the presence of avian flu in the state on April 20.
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