Synchronized migration could endanger the eastern whip-poor-will

Scientists at Ohio State University have made some new discoveries while tracking eastern whip-poor-wills with GPS tags during their annual migrations. Although the birds come from many places – ranging from northern Wisconsin to southern Ontario – they all follow the same pathway south to their wintering grounds in Mexico and Central America. In fact, the birds stick relatively close as they travel. 

The research, which was led by OSU graduate student Aaron Skinner, showed that the eastern whip-poor-will population was concentrated within 300 miles of each other in Oklahoma, Arkansas and East Texas during a single day. 

Being all in one area leaves the birds vulnerable to a single threat. This is particularly concerning because the eastern whip-poor-will population has already dropped by 70 percent in recent years. 

“About half of the entire population of whip-poor-wills breed in the Midwest, and our findings indicate their migration south is very synchronized,” explained study co-author Professor Christopher Tonra. 

“That suggests we have to protect the forested habitat in that small area of Oklahoma, Arkansas and east Texas, which is a vital migratory stopover. And we must find ways to protect the birds as they all move through the highly urbanized areas of east Texas.”

The whip-poor-will is an iconic nocturnal bird, seldom seen but known (and named) for its unique call. For the investigation, the scientists captured and tagged birds from five breeding areas in four states: Wisconsin, Illinois, Ohio and Missouri. 

The birds were fitted with GPS tags that tracked their movements, and were recaptured for data collection when they returned the next year. Out of 115 whip-poor-wills that were tagged in 2017 and 2019, 52 individuals yielded useful data.   

Professor Tonra noted that while the overall population of whip-poor-wills is in decline, populations in some breeding areas in the United States are relatively stable, and other populations have disappeared altogether.

This fact, coupled with the finding that nearly all the birds wintered in the same area, suggest that whip-poor-wills may face their greatest challenges here in their U.S. breeding grounds, said Professor Tonra. 

“If the wintering grounds were the major problem, we should see similar population declines in all their different breeding areas, which is not what is happening,” he explained.

The experts speculate that one issue could dwindling insect populations across some U.S. breeding sites. Whip-poor-wills are insectivores that eat moths, fireflies,  beetles, and other flying insects. 

The research is an important step toward understanding and hopefully halting the decline of the eastern whip-poor-will.   

“I associate whip-poor-wills with camping in eastern forests and hearing them call through the night,” said Professor Tonra. “The idea of them disappearing is very alarming, and we’re trying to learn more about what may be causing their decline.”

The study is published in the journal Diversity and Distributions.

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By Zach Fitzner, Earth.com Staff Writer