Approximately 30,000 islands can be found in the Great Lakes. They range in size from less than an acre to more than 140,000 acres (Isle Royale). The basin’s islands contain virtually all the unique natural features associated with the Great Lakes shoreline as well as some of the last intact ecological communities found in the Great Lakes.
Great Lakes islands support rare, threatened and endangered species due in part to their biological diversity, isolation from human disturbance, and absence of invasive species. A number of colonial waterbirds, such as common tern, and black-crowned night heron nest on Great Lakes islands at sites free from predators and other disturbances.
Shoals surrounding the islands are of high value to Great Lakes fish. Many islands are also considered important stopover sites for neotropical migratory songbirds that pass through the Great Lakes in vast numbers each year.