New UMaine Study Highlights Annual Migration of Red-throated Loons in the Eastern United States – UMaine News

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Red-throated Loons are known for their superior fishing abilities, but little is known about the migration patterns of this waterbird in eastern North America. A University of Maine study is the first to identify four red-throated loon migration routes along the Atlantic coast of North America and their breeding grounds in the High Arctic, giving advocates environment a clearer picture of how to conserve the bird.

Understanding a species’ migratory patterns is key to understanding its population dynamics, as impacts that occur during migration can ripple through each local population. As such, effective conservation of a species also requires an understanding of these migratory dynamics to determine key areas for animal support and potential threats to the ecosystems therein.

“If you want to keep loons in a lake, you have to understand all the other waters that those loons depend on,” says Brian Olsen, professor of ornithology in UMaine’s School of Biology and Ecology and the one of the authors of the study. “Each bird is supported by its own band of the mainland – from its summer lake, to its winter ocean grounds, to the offshore shore where it stops for a few weeks on each migration to rest and fish. . If something goes wrong anywhere in this strip, the loon could disappear from the entire strip. »

By tagging the birds with satellite transmitters, researchers at the University of Maine tracked red-throated loons for a year along their migratory routes from the mid-Atlantic coast of the United States to their breeding grounds in the United States. ‘Arctic. The red-throated loon is listed by the U.S. Fish and Wildlife Service as a species of conservation concern in both its Arctic breeding range and the wintering grounds of the Atlantic Flyway. The objectives of the study were to provide more precise information on the use of space during the annual cycle of the species in this sensitive area.

The researchers also looked at the strength of what’s called “migratory connectedness” in the species, or the likelihood that birds that breed next to each other will also winter next to each other and use pathways. similar migration routes to get there. Species with high migratory connectivity may be particularly affected by changes along migratory routes, as any disturbance affecting one bird is likely to affect several of them.

Finally, the researchers used existing migration theories to build a species movement network to better understand the areas the birds frequent along the route and how they use them.

UMaine researchers have found four discrete migration routes for red-throated loons wintering on the Atlantic coast; some ended in Canada and some in Greenland, some went straight up the Atlantic coast and some circled the Great Lakes. There were key stops in areas that served as hubs for birds along these routes, such as James Bay and lower Hudson Bay, southern Great Lakes, Gulf of St. Lawrence , Nantucket Shoals, and major mid-Atlantic bays like Delaware Bay, Chesapeake Bay, and Pamlico Sound.

Despite sampling only 5% of the breeding range of the North American Atlantic coast, an area equivalent to only 0.001% of the presumed breeding range of the Atlantic Flyway, the birds studied are distributed over 65% of this breeding range, suggesting that the mid-Atlantic region forms the core of the red-throated loon’s non-breeding range that winter. The scattered migration also suggests that migratory connectivity is low, but anthropogenic disturbance or changing environmental conditions in a relatively small area of ​​the wintering range could impact much of the North American breeding range. .

Carrie Gray is a boreal researcher for the National Audubon Society and the lead author of the study, which she conducted while earning her doctorate. at UMaine. Gray explains that when the size of the wintering range is small compared to the size of the breeding range, it means that a higher proportion of the population may experience the effects associated with environmental changes in that range. ‘wintering.

“This can lead to a positive outcome, for example, if the regional abundance of forage fish is above average one winter and the birds experience a productivity boom the following summer. On the other hand, as climate change causes ocean temperatures to rise and the distribution of forage fish shifts northward to follow the colder waters to which they are adapted, this means that birds that depend on these fish also have to move north,” says Gray. “Monitoring studies that follow individual Red-throated Loons over several years are needed to assess to what extent they are ‘hardwired’ to migrate to specific wintering areas, or whether their movements during the non-breeding season are flexible and allow them to respond to local conditions to track their resources.

There were also a few migration staging points that seemed of critical importance to the species. For example, 90% of birds tracked in the spring and 61% tracked in the fall depended on a small number of primary use areas along the Atlantic coast of the northeast Maritimes of the United States and Canada. Factors that could impact loons in these areas could include exposure to contaminants and oil spills, risk of collision mortality and habitat displacement due to offshore wind farms, threat of by bycatch associated with fishing nets and bad weather.

“A fishing boat off the Nantucket Banks is probably there for the same reasons the birds are,” Olsen says. “Productive currents benefit the fishery for both. But although the ship’s operator may notice a handful of loons working in the same waters as them, our study suggests that if they go there every day for a few weeks, they might see a large proportion of all birds of the Atlantic coast of North America as they move through the region. There are only a handful of hotspots like this, and this study is the first to describe where they are.

Future multi-year studies are needed to determine if the same birds use the same migratory route each year, which is also important for understanding how easily ecological disturbances might impact the red-throated loon population. However, the results of this study – published in the Journal of Ornithology in August 2022 – will not only inform efforts to protect the red-throated loon, but highlight the importance of examining large-scale migratory patterns for conservation in general.

“Tracking studies allow us to follow birds through their incredible migratory journeys and discover the places they depend on throughout the year. We need this information to identify habitats that need to be protected to maintain bird populations. I am delighted that we have been able to expand on some of this knowledge as it relates to red-throated loons and I am encouraged to see, increasingly in our field, an increased focus on bird conservation on a hemispheric scale,” said Gray said. .

Contact: Sam Schipani, samantha.schipani@maine.edu

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