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Audubon Great Lakes Equips Small Tracking Devices to Study Michigan’s Vulnerable Black Terns

‘NanoTags’ Helping Researchers to Understand the Marsh Birds’ Steep Population Declines Over the Past Half-Century

MICHIGAN (September 29, 2021) – A Michigan Species of Special Concern, the Black Tern has experienced a dramatic population decline over the past 50 years, with up to 70 percent of the population lost in the state.  Researchers at Audubon Great Lakes are using small tracking devices called NanoTags to lead the effort to study and understand what is driving this decline and to develop conservation strategies that can help bring these elegant marsh birds back.

“Black Terns face an uncertain future in Michigan. By tracking whether Black Terns successfully fledge and depart their breeding grounds, we can better understand whether the cause of their population decline is from low chick productivity or low adult survivorship,” said Erin Rowan, Senior Coordinator, Michigan Conservation for Audubon Great Lakes. “NanoTags also shed light on where Black Terns are thriving along their migration route, and where they’re struggling. The hope is that we can better understand why we’re seeing such dramatic declines in populations and develop conservation strategies to reverse that decline.”

Black Terns nest and breed in the coastal and inland marshes of Michigan in the summer, where they build their nests on floating mats or rafts of dead, crushed bulrush and cattail. This summer, Audubon Great Lakes and partners visited Black Tern nests to attach NanoTags to 28 pre-fledged Black Tern chicks at St. Clair Flats State Wildlife Area and Wigwam Bay State Wildlife Area in Southeast Michigan.

To pick up signals from the bird’s tiny radio transmitters, researchers built a 20-foot Motus Tower at each of the sites, with the addition of the Wigwam Bay, City of New Baltimore, and Lake St. Clair Metropark towers this past year. These metal radio towers allow researchers to track Michigan’s Black Terns with high precision, and due to the growing network of towers across the globe, over great distances. The first tower at St. Clair Flats was launched in 2017 by Environment Canada as part of the Motus Wildlife Tracking System, an international collaborative network of researchers that use automated radio telemetry to track numerous wildlife species. 

Over the last two months, Black Terns have been traveling on their annual migration journeys from their breeding grounds in Michigan to their wintering grounds in the coastal areas of Central and South America. Researchers have been monitoring the tagged birds to measure the fledging success of chicks and migration patterns, including the locations birds are using to rest and refuel. You can explore the tracks, or pathways, that Black Terns and other tagged birds have taken by exploring the Motus Tracks database and selecting “map” to view the movements of tagged birds over time.  

Between 2019 – 2020 researchers deployed 19 NanoTags at St. Clair Flats State Wildlife Area and Wigwam Bay State Wildlife Area. Researchers were also able to detect the best and clearest path of an individual Black Tern to date.

“Our early analysis shows that Black Tern colonies in the Great Lakes are successfully producing young, with more chicks likely fledging than we can observe on the ground,” said Sarah Saunders, Quantitative Ecologist for National Audubon Society.  “By tagging more birds and adding additional towers this year, later this fall we hope to have an even clearer picture on how many birds are fledging, where they are going during migration, and how long they are on the move.” 

Audubon Great Lakes Black Tern NanoTagging and monitoring is made possible by partners Michigan DNR, Detroit Audubon, Environment Canada, Indiana University, University of Michigan, Common Coast Research and Conservation, Upper Mississippi Great Lakes Joint Venture, Kalamazoo Nature Center, and Detroit Zoo.

In addition to NanoTagging, Audubon Great Lakes and partners have studied Black Terns at St. Clair Flats State Wildlife Area since 2013 with the primary goals of estimating colony size and breeding success. Researchers band adult and juvenile birds. This year, Black Tern monitoring expanded across the state as 35 volunteers surveyed historical breeding sites to best identify active breeding locations, chick hatching success, and habitat quality in an effort to identify priority areas for restoration and monitoring. Wetland restoration aimed at improving or maintaining habitat quality is also ongoing at several colonies.

TO REQUEST AN INTERVIEW: Nicole Minadeo,, 419-308-4846

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The National Audubon Society protects birds and the places they need, today and tomorrow. Audubon works throughout the Americas using science, advocacy, education, and on-the-ground conservation. State programs, nature centers, chapters, and partners give Audubon an unparalleled wingspan that reaches millions of people each year to inform, inspire, and unite diverse communities in conservation action. A nonprofit conservation organization since 1905, Audubon believes in a world in which people and wildlife thrive.

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