What happens when a nocturnal migrating songbird gets lost over Lake Erie?
New research indicates that it might rely on archipelagos like North, Middle and South Bass Islands as a navigation aid or resting place.
“Lake Erie is a barrier for migrating birds. It’s not huge like the Gulf of Mexico, but there are 30 to 40 miles between Ohio and Canada, and a bird that gets in trouble over water is going to have a large problem,” said Verner Bingman Distinguished Research Professor of neuroscience in the Department of Psychology at Bowling Green State University.
Although Lake Erie is a topographical barrier, many songbirds will cross it during their nocturnal migrations. However, the island archipelago in the central-western basin of Lake Erie could potentially be used to ameliorate some of the possible negative consequences of a lake crossing, such as a greater risk of wind-drift over emptier parts of the lake, as well as offering a safe landing area should dangerous weather arise. The islands also offer landing habitat for birds caught over the lake as dawn approaches.
In research funded by Ohio Sea Grant, Bingman and Murphy Harrington, a master’s degree student in biology, set up infrared cameras last fall on Middle Bass Island to detect the directions of movements of individual nocturnal migratory birds, such as warblers, vireos, thrushes and sparrows.
The research aimed to determine whether the birds are using the islands to adjust their path of flight in an active way. Bingman and Harrington compared the results to individual birds migrating over Bowling Green and groups of birds, detected by Doppler radar, migrating over Cleveland.
They found that the nocturnal migrating songbirds move in a south/southwest direction, but there is little night-to-night variation in their movements. The paths of individual birds over Bowling Green are more spread out and over Cleveland oriented in a different direction.
“So this indicates that birds are actually using those islands to maintain direction, and once they’re over the land, like in Bowling Green, they don’t have a reliable ground reference to account for error,” Bingman said. “They seem to be following the islands as a leading line to maintain a preferred migratory bearing. An additional adaptive benefit to following the islands is that should inclement weather arise, they could get themselves out of trouble.”
Harrington, who is interested in conservation and dreams of someday working with endangered species, spent nearly a month of lonely nights taking observations or more than 500 single migratory birds flying over Middle Bass Island and up to 200 over Bowling Green. She had to watch the camera so intently that she couldn’t do much else other than listen to podcasts, but often she just sat and enjoyed the quiet. She said she loved doing it.
“On windier nights the birds would zoom along being carried by the wind and passing by really quickly,” she said. “I passively listened to migrating birds’ calls, but it often was windy and I was close to the waves, which kept me from hearing them. On really calm nights you could definitely hear them passing, which was so cool.”
A birder interested in ornithology, Harrington sometimes referenced the website BirdCast, which forecasts migration in real time, to help predict her success.
“Sometimes I would sit out for four hours and see two birds,” Harrington said. “But there was a night where I got one every minute for three hours. There were nights I would easily get 100-150 birds.”
Bingman plans to continue statistical comparisons and repeat the study this spring and fall as well as next spring in order to have two years of data. Next spring and fall, he also plans to make ground-based observations on the flight directions of the songbirds in the early morning to see if the birds arrive from all directions to use the land as an oasis for rest.
The research could contribute to better strategies to manage environmental topography for migration.
“The migrations are an important source of economic activity around Lake Erie. Thousands of people come in to watch the birds. We could develop policies to support this,” Bingman said.
“I loved working with Vern, and I knew I’d come out of the experience learning about something I knew nothing about, like neuroscience and migration,” Harrington said. “I liked the idea, too, of knowing not only what motivates the choices that migrating birds are making, but once you understand what is driving their choices, you can narrow in to things I’m interested in like protecting stopover habitats and making efforts to preserve bird habitats.”
This research also has relevance for wind turbine development in Lake Erie because of the importance of Ohio and Lake Erie for migratory birds, particularly small songbirds,” Bingman said. “Should there be development, this kind of data could inform policymakers and developers if they are going to put turbines in Lake Erie — where should they put them, where environmental impacts would be the least. From our research: You don’t want them anywhere near the islands.”