Many endangered and threatened water birds, such as the endangered common tern, typically nest on barren islands or remote beaches to avoid mammalian predators, including people. There is one such site on Lake Butte des Morts on property owned by the Butte des Morts Conservation Club. It is an island in Samers Bay about ¼ mile south of the Terrell’s Island peninsula. This island was formerly just a small rock pile only a few feet in diameter. In 2006, the club teamed up with the Wisconsin Department of Natural Resources, the U.S. Fish & Wildlife Service, and the Lower Fox River Green Bay Natural Resource Trustee Council to rebuild the island with a 30 x 40 foot rock base topped with sand; ideal nesting habitat for common terns. This island brought nesting common terns back to Winnebago County, and they have nested there with varying degrees of success ever since.
“Varying degrees of success” of course means the birds have occasionally encountered problems on the island. These include vandalism, crowding by pelicans and cormorants, and predation from mink and owls (at least one mink once swam ¼ mile out to the island). Even a little vegetative growth at the start of the nesting season will cause the birds to look elsewhere for a more suitable nest site.
All of this means fairly specific management. In the case of the common tern island, that means annually installing and removing fencing around the perimeter of the island to keep out larger water birds such as pelicans and cormorants, and mammalian predators such as mink and otters. It also includes manipulating vegetation, and installing signage advising people to stay off the island during the nesting season from April through July. In the end, however, the sight of young common terns on the wing (indicating a successful hatch) is well worth the effort.