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McKearnan, J.E. 1986. Status and breeding success of common terns in Minnesota. M.S. Thesis, University of Minnesota. 53 pp.


Recent concern about the population size of Common Terns (Sterna hirundo) in the Great Lakes region led to a two-year study on the status and breeding success of Common Terns in Minnesota. All known colonies were censused in 1984; breeding success was monitored at the Duluth sites in 1983 and at all sites in 1984. Colony sizes ranged from 20-489 pairs and approximately 880 pairs of terns nested in Minnesota in 1984; the current breeding population is estimated to be a third the size of the Common Tern population in Minnesota in the 1930's. Breeding success was estimated at 0.15 fledgings/pair; 6% of the eggs laid survived to fledging. Assuming no immigration occurred, Minnesota terns did not produce enough young during the study to maintain the current population size. Factors contributing to nest failure included: storm damage, use of poor quality nesting habitat, predation, nest site competition with gulls and human disturbance. Recommendations for conservation and management include population monitoring, protection and enhancement of tern breeding habitat and exclusion of breeding Ring-billed Gulls (Larus delawarensis) from tern nesting sites, and monitoring of contaminant levels in lakes adjacent to nesting areas.

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