Lake Superior Common Tern Conservation Final Report

Abstract

Since its creation, Interstate Island has lost approximately two acres of useable tern nesting habitat, primarily due to wind and water erosion. In 2015, the Minnesota Department of Natural Resources (DNR) added 3,000 cubic yards of clean sand and pebbles to the island to mitigate the effects of erosion and fluctuating water levels, which has caused seasonal flooding of nesting sites. This restoration effort should make the island more suitable for nesting Common Terns, although more restoration work is needed. Interstate Island is a Wildlife Management Area jointly managed by the Minnesota and Wisconsin Departments of Natural Resources (DNR), with the primary objective of providing suitable nesting habitat for colonial waterbirds. Since 1990, this has been the only nesting location of Common Terns in the St. Louis River Estuary with roughly 200 breeding pairs. Interstate Island is also the primary breeding location of Ring-billed Gulls (Larus delawarensis) in the area, with an estimated 13,000 breeding pairs. The rapidly increasing population of Ring-billed Gulls has drastically reduced available breeding habitat for Common Terns. This species competes for breeding space with terns, depredates eggs, and preys on tern chicks. In some years the colony has had total nest failure, primarily due to intense predation by gulls.