GREAT OUTDOORS: Avian flu a threat to bald eagles

The bald eagle population has made a significant recovery since 1979 when only four active nests remained in Ohio as a result of chemical pollution that prevented successful reproduction. Now I can count on seeing some during every visit to the western Lake Erie area, especially around the coastal marshes, Sandusky Bay and the major tributary streams. The Ohio Division of Wildlife recently reported that after conducting aerial surveys, they have confirmed 964 actively nesting pairs across the state. Hundreds of additional immature birds exist statewide. However, even with a population in the low thousands, bald eagles are still vulnerable to catastrophic events, such as storms and diseases that can reverse gains made by this slow-to-reproduce species. West Nile Disease carried by infected mosquitos often becomes debilitating or fatal to bald eagles, but Dr. Bill Bowerman of the University of Maryland says Highly Pathogenic Avian Influenza (HPAI) is proving to be much worse. He has studied environmental contamination in eagles for over 40 years. It arrived in North America in the fall of 2021 when the H5N1 strain jumped from Europe to Iceland, then into Canada. The biggest carriers are waterfowl, such as ducks, geese and swans, then shorebirds, including gulls, terns and waders. To illustrate how catastrophic this disease can get in the wild, a kayaker discovered more than 30,000 dead geese from HPAI in the Northwest Passage in 2022. Bowerman said that prior to 2017, the leading causes of bald eagle deaths included vehicle collisions (69%), poisoning (15%, 95% from lead), disease (8%) and less than 5% from electrocution, gunshots/traps and starvation. But in 2022, of 222 eagle carcasses collected, fatalities from vehicle collisions dropped to 48% while disease jumped to more than 40%. HPAI was confirmed in 71 eagles that year. The northern part of Michigan, where more than 500 eagles gather when huge flocks of waterfowl come through during their fall migration, was the most affected. During the spring of 2022 on Lake Superior, Bowerman and the pilots who monitor eagles noticed that signs of nesting activity were conspicuously absent. He estimates that Michigan lost 40% of its nesting pairs. Where they normally collect blood samples from about 90 eaglets each spring to test for environmental contaminants, they were only able to obtain seven. Numbers of diseased birds dropped in 2023 and 2024, but there have been 18 confirmed HPAI deaths plus another 16 awaiting lab results so far this year. During March and April 2022, several eagle HPAI deaths were confirmed in northern Ohio and only 48% of nests were successful. As was the case in Michigan, 2023-2024 was quiet with respect to HPAI. However, late last fall, I heard of dead eagles, a snowy owl and other bird species being found and reported by trappers operating in the marshes along Lake Erie. According to Mike Reynolds, executive administrator of Wildlife Management, ever since the earliest outbreaks seen in 2022-2023, the biggest carriers and mortalities come from Canada geese, sometimes hundreds at a time. This spring, he says black vultures are also being affected. They feed on carcasses of infected birds, including deceased members of their own species. Of the 13 dead bald eagles from 10 Ohio counties (especially from the northeast and southwest parts of Ohio) submitted to the National Veterinary Services Laboratory in Ames, Iowa, this year, 11 tested positive for HPAI with the other two had undetermined causes of death. Fortunately, the effect of HPAI on Ohio's bald eagle population is not yet considered significant.