Distribution and abundance of nesting common and Caspian terns on the North American Great Lakes, 1976 to 1999

R. D. Morris, D. V. Weseloh, Francesca J. Cuthbert, C. Pekarik, L. R. Wires

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19 Scopus citations


Canadian and US federal wildlife agencies completed three surveys (1976-1980, 1989-1991, and 1997-2000) to census colonial waterbirds breeding on the Great Lakes. We here summarize and comment on nest numbers and colony site distribution of common terns (Sterna hirundo) and Caspian terns (Hydroprogne caspia). Common terns are in serious trouble on the Great Lakes. Numbers declined with substantial losses in nests (- 19.1%) and colony sites (- 23.2%) between the first and third censuses. An increase in numbers at US sites (+ 26.6%) did not compensate for losses (- 33.1%) at Canadian sites. Caspian terns increased in nest numbers (+ 65.9%) and colony sites (+ 50.0%) over the same period. The increase at US sites (136.5%) was greater than at Canadian sites (11.5%). Most (70.7%, n = 186) common tern sites had nests during only one census; 17 sites (6.5%) had nests during all censuses. In contrast, 9 of 33 (27.2%) Caspian tern sites had nests during all censuses and contained a majority of nests (50-82%) in each census. Pairs of both species nested on natural substrates across the Great Lakes. Common terns nested mostly on artificial (human-constructed) substrates on the lower Great Lakes. We identify site characteristics that may have contributed to long-term (three census) occupancy by common terns (small size, artificial substrates, absence of ring-billed gulls) and Caspian terns (natural substrates on large, remote islands). We suggest an urgent need for protection and conservation of common tern colonies and identify specific priority sites for implementation of management protocols.

Original languageEnglish
Pages (from-to)44-56
Number of pages13
JournalJournal of Great Lakes Research
Issue number1
StatePublished - 2010

Bibliographical note

Funding Information:
We offer a special note of acknowledgement and appreciation to Hans Blokpoel, Gaston Tessier, Bill Scharf and Gary Shugart for their vision in the mid 1970s to initiate the Great Lakes waterbird census program, and to continue it through the late 1980s. We especially thank Kate Gee for drafting the figures. We also thank Tania Havelka, Glenn Barrett, Dave Moore and Kim Williams for fieldwork and/or data management. Funding for the Binational Colonial Waterbird Survey was provided by the Canadian Wildlife Service and the US Fish and Wildlife Service. Logistic support was provided by the University of Michigan Biological Station and the Canada Centre for Inland Waters. Insightful comments from two anonymous reviewers and Martin Stapanian greatly improved the final version of the manuscript.


  • Breeding biology
  • Caspian tern
  • Common tern
  • Great Lakes
  • Hydroprogne caspia
  • Population numbers
  • Sterna hirundo


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