Management efforts for the conservation of common tern Sterna hirundo colonies in the Great Lakes: Two case histories

Abstract

Numbers of common tern Sterna hirundo colony sites have declined throughout the lower Great Lakes since the early 1970s. For the past 10–13 years, we have developed and tested management procedures to maintain numbers of breeding pairs. At an insular colony site near Port Colborne on Lake Erie, management procedures included protection from human disturbance, substrate rehabilitation, prevention of nesting on tern substrate by ring-billed gulls Larus delawarensis and control of egg/chick predation by ring-billed and herring L. argentatus gulls. At the Eastern Headland in Lake Ontario, management efforts included vegetation control, monofilament lines to prevent nesting by gulls, control of human disturbance, and construction of new nesting habitat. Success in maintaining numbers of breeding pairs was high at Port Colborne but poor at the Eastern Headland. We discuss probable reasons for the differences in success at the two colonies. As extirpation of a species from broad geographic areas may often begin with isolated local declines in numbers of breeding pairs, regular management procedures at local colonies are desirable.