Researchers studying the Cerulean Warbler made a breakthrough last spring. For the first time, they were able to track the bird’s epic northward migration. As a result, we now know much more about the places that must be conserved to reverse the warbler’s decline. The species has shrunk 70 percent over the past 50 years.
In early 2016, 19 males were outfitted with geolocators, high-tech backpacks that capture light data associated with daily sunrise and sunset, information that helps map an individual’s migration route.
One of the birds was dubbed Elmer. His journey offers insights into the threats driving the species’ decline.
He spent the winter in Colombia, the destination for many Cerulean Warblers. Forests there are under threat. About 200,000 hectares — an area greater than 200,000 football fields — are destroyed annually.
Elmer took off on March 20. Over six weeks, he would travel thousands of miles. He touched down first in Guatemala, where he spent three weeks fattening up before flying straight across the Gulf of Mexico.
He avoided the 2,500 oil and gas platforms that are lit up at night as a warning to boats and aircraft. Especially in bad weather, birds become attracted to the lights and may circle them for hours, depleting the energy needed to complete the journey.
Refueling in central Tennessee, Elmer bypassed the big cities and tall, reflective buildings that confound migratory birds. He also avoided house windows and free-roaming cats, which kill some 2.4 billion birds every year in the U.S. alone.
Against the odds, the warbler arrived on his breeding grounds in northwestern Pennsylvania in May, right on schedule. What did he do first? He flew to his namesake elm tree, where he had nested the year before, and started to sing.
The Cerulean Warbler Geolocation Study is a collaboration among ABC, the University of Tennessee, Arkansas State University, Indiana University of Pennsylvania, and the Northern Research Station of the USDA Forest Service.
A version of this article appeared in the April 2017 issue of BirdWatching magazine.
This story was provided by American Bird Conservancy, a 501(c)(3), not-for-profit organization whose mission is to conserve native birds and their habitats throughout the Americas.
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