Fish and Wildlife Service, Wisconsin.
Gravel Island (4 acres) and Spider Island (23 acres) comprise Gravel Island National Wildlife Refuge. These islands are located in Lake Michigan, approximately one mile to the east of the Door County Peninsula of Wisconsin. Gravel and Spider islands were initially protected in 1913 by an Executive Order with the intent to preserve native bird breeding habitat. Herring gulls and double-crested cormorants nest on these islands. Gravel Island also supports a large nesting population of Caspian terns, historically the largest colony in the Great Lakes region.
In 1970, the United States Congress designated Gravel, Spider and Hog (part of Green Bay National Wildlife Refuge) islands as the Wisconsin Islands Wilderness Area which at 29 acres, is one of the smallest wilderness areas in the country. The prime management consideration of the wilderness status was the continued protection of nesting birds by limiting access to the islands during the breeding seasons. For this reason, the wilderness islands are closed to public visitation consistent with the conservation purpose of the refuge. The wilderness designation provides an additional level of protection on the islands and boaters are asked to stay at least a quarter mile offshore so as not to endanger the nesting areas.
Public use is not allowed due to ground nesting by migratory birds and limited access. For further information please contact staff at the Horicon National Wildlife Refuge Complex in Mayville, WI. Contact (920)387-2658 or greenbay@fws.gov. The office/visitor center is located on the east side of Horicon Marsh, 3.5 miles south of State Highway 49 on County Road Z.