This large treeless island was once used for bombing practice by the U. S. Military. Today, the island is best known as a national wildlife refuge with an abundance of seabirds.
As a breeding area, this site is truly special with a diverse mix of nesting terns, Black Guillemots, and Atlantic Puffins. Seal Island also supports one of the largest colonies of Great Cormorants in the state.
The key threat to this site would be an oil spill during the breeding season. Ecotourism, based out of Bar Harbor, has increased in recent years though no known negative effects have been documented.
The island is owned by the U. S. Fish and Wildlife Service, Maine Coastal Islands National Wildlife Refuge. The island is closed to the public during the seabird nesting season (April 1 to August 31).