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Bald eagles are threatened by avian influenza

After their near extinction in the 1960s, bald eagle populations rebounded significantly – a phenomenon considered by many scientists a massive conservation success story. However, a recent study led by the University of Georgia (UGA) has found that a highly pathogenic strain of avian influenza – known as H1N1 – is currently killing an unprecedented number of bald eagles, thus endangering once more this species.

According to the researchers, in 2022, under half of bald eagle nests along coastal Georgia successfully fledged at least one eagle, which is 30 percent below average for this region, while in a county in Florida, the success rate of nests was halved, decreasing from 86.5 percent to 41 percent.

“We had reports from people who faithfully monitor eagle nests year after year with these heartbreaking stories of an adult eagle found dead below their nest. Within a few days, often its mate and the chicks were also found dead below the nest. It is clear the virus is causing nest failures,” said study lead author Nicole Nemeth, an associate professor of Veterinary Medicine at UGA.

The first cases of avian influenza in bald eagles were confirmed in April 2022. Since then, the number of cases has skyrocketed, with infections reported not only in bald eagles, but also in a variety of other birds, including vultures and other raptors, waterfowl such as ducks and geese, aquatic birds like pelicans and herons, commercially farmed poultry, and even some songbirds. While 6,200 cases have been officially reported across the U.S., this number is most likely an undercount.

“I think the number of wild bird cases is drastically underreported. People will submit one snow goose, for example, and it will test positive for the virus. And then they’ll tell you, ‘Well, there are thousands of geese dying at the same site.’ But it only goes down as one infected bird,” Nemeth explained.

Since the virus can persist in water for over a year, the birds most at risk of infection are those living in coastal or other aquatic areas, or those that prey on birds living in such environments. Birds can catch the virus from spending time in the water and carry it to new locations during their migration, while raptors such as eagles or vultures can pick it up when they consume infected birds. Moreover, the virus has also spread to wild mammals, such as red foxes, coyotes, racoons, opossums, seals, and even some bears. While the risk posed to humans remains low, many of these species could experience significant declines.

“A virus that can spread and be maintained as this virus can, it’s everywhere now. We can’t contain the virus, and we can’t vaccinate wild birds. But we can document the losses and try to help conserve affected species and populations the best we can,” Nemeth concluded.

The study is published in the journal Nature Scientific Reports.

By Andrei Ionescu, Staff Writer

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