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Distribution and Numbers of Common Terns on the Lower Great Lakes during 1900-1980: A Review

Peter A. Courtney and Hans Blokpoel
Colonial Waterbirds
Vol. 6 (1983), pp. 107-120
Published by: Waterbird Society
DOI: 10.2307/1520977
Stable URL: http://www.jstor.org/stable/1520977
Page Count: 14
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Distribution and Numbers of Common Terns on the Lower Great Lakes during 1900-1980: A Review
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Abstract

In the lower Great Lakes area at least 58 Common Tern (Sterna hirundo) colonies, each containing 50 or more nests, have existed during 1900-1980 or were still active in 1980. Estimated nest numbers increased from 4,000-7,000 (during 1900-1920) to a peak of 16,000 in the early 1960s and then declined to 5,000 in the late 1970s. These population changes were greatly influenced by the rise and decline of the ternery at Gull Island, Presqu'ile Provincial Park. Historical data show a shift from western Lake Erie and eastern Lake Ontario as a major breeding area to eastern Lake Erie and western Lake Ontario and the Niagara River. A shift towards the use of man-made sites for nesting has occurred and in 1980 about 70% of all Common Terns nested on seven man-made sites. Permanent desertion by Common Terns of their colonies has resulted from (1) encroachment by vegetation and/or nesting gulls (Ring-billed Gulls Larus delawarensis and Herring Gulls L. argentatus), and (2) recreational and/or industrial activities by man. The following factors have affected reproductive success: predation by birds and mammals, human disturbance and pollution of the terns' aquatic environment. The Great Lakes Common Tern population appears to be fairly discrete with little emigration or immigration taking place. Recently, the weighted mean fledging success for different colonies and different years was 0.89 chicks fledged per nest (virtually the same as the published figure for Massachusetts terneries).

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