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New Audubon Study Reveals Prothonotary Warbler 5,000 Mile Migration Path For First Time

Scientists Uncover Clues to Mysterious Prothonotary Warbler Decline

NEW YORK (August 31, 2015)- New findings in a study by the National Audubon Society and Louisiana Bird Observatory (LABO) reveal the first-ever mapped migration of a Prothonotary Warbler, a species of conservation concern. A paper published this week by the Journal of Field Ornithology, highlights an enhanced understanding of the year-round journey of this charming songbird.

“Knowing where these birds go and how long they stay at each location will help us understand what conservation actions will most effectively reverse population declines,” said Dr. Erik Johnson, study co-author and Director of Bird Conservation for Audubon Louisiana. “This research has already resulted in several exciting discoveries.”

The Prothonotary Warbler population has declined 40 percent since the 1960s and the preferred breeding habitats – swamps and forested wetlands – are also disappearing at an alarming rate. One fourth of the global population (1.6 million estimated) breeds in Louisiana. The rate of decline in birds from this region is even more rapid according to scientists, up to 50% since the 1960s, and the cause is unknown. The species’ overall decline has outpaced that of their breeding habitat and scientists suspect these birds are experiencing difficulties elsewhere, including on their wintering grounds in Central America and northern South America. This most recent study adds to a growing body of work intended to better understand factors driving their population declines.

“As part of this study, in 2013, we deployed three geolocators on Prothonotary Warblers in Baton Rouge,” said Dr. Jared Wolfe, study co-author and founder of the Louisiana Bird Observatory. “After the 2013 breeding season, at least one individual completed its fall migration, overwintered and finally made his way back to Louisiana in 2014 where the bird was recaptured and the geolocator was retrieved.”

For their small size – typically weighing just half an ounce – these bright yellow warblers are incredible travelers and impressively resilient. Data from the single returning male bird in 2014, named “GeoDad,” shows he had migrated south for over three months to spend his winter in northwest Colombia. Amazingly, GeoDad’s tracker shows that it took him just three weeks in March to return to Baton Rouge from Colombia. In only eight months, he traveled a minimum of 5,000 miles, through 7 countries and made three significant nonstop water crossings—twice over the Gulf of Mexico and once over the Caribbean Sea.

Wolfe and Johnson have been working for several years with several other scientists and a host of dedicated LABO volunteers to monitor and band these birds, but tracking their migration has been a challenge. On songbirds that are too small to carry GPS units, scientists use geolocators, mini high-tech backpacks, which weigh much less. A geolocator records the estimated longitude and latitude of a bird, but the data cannot be wirelessly or remotely transmitted, and are stored on the device until they can be retrieved from the bird and manually downloaded.

Based on the success of this study, the Prothonotary Warbler Working Group was formed, a coalition coordinated by Johnson. The Working Group includes partners from Audubon South Carolina, Virginia Commonwealth University, Arkansas State University, Ohio State University and about 20 other organizations. Johnson hopes to have 10 sites sending out 10 or more tagged birds over the next couple of years to help inform an international conservation plan.

Since 2014, the group has already deployed 77 geolocators on Prothonotary Warblers across five states. Interestingly, early indications from some of these is suggesting that several birds from Louisiana took nearly twice as long to get to their wintering grounds in South America than a single bird tracked by researchers from Audubon South Carolina. The geolocators are starting to paint the picture of how different populations are migrating. By increasing the breadth of the study, the team hopes to better understand the migratory and overwintering behavior to identify core areas of habitat use that may require additional management and protection.

Audubon and LABO will continue building and installing nest boxes, training new citizen scientists and building awareness to help monitor Prothonotary Warbler populations. The presence of these nest boxes has strengthened some populations in current years by excluding predators and parasitism from cowbirds that are notorious for sneaking their eggs in warbler nests. For more information and updates about ongoing efforts to save Prothonotary Warblers, visit La.Audubon.org.

The National Audubon Society saves birds and their habitats throughout the Americas using science, advocacy, education and on-the-ground conservation. Audubon's state programs, nature centers, chapters and partners have an unparalleled wingspan that reaches millions of people each year to inform, inspire and unite diverse communities in conservation action. Since 1905, Audubon's vision has been a world in which people and wildlife thrive. Audubon is a nonprofit conservation organization. Learn more at www.audubon.org and @audubonsociety.

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