More than 150 species of birds and four species of mammals have been observed using the islands. Several other species of birds, mammals, amphibians and reptiles are suspected of using the islands because they are present in the surrounding areas and the islands provide suitable habitat. The larger islands host the greatest number and diversity of species. These islands support numerous species of colonial nesting waterbirds such as ring-billed and herring gulls, great blue herons, great egrets, black-crowned night herons, double-crested cormorants and Caspian and common terns. Other bird species found breeding on these islands, include spotted sandpipers, killdeer, and a variety of waterfowl, raptors and songbirds.