This treeless island lies to the west of Isleboro and east of Northport. This site is an important seabird nesting island in the upper portion of Penobscot Bay.
For many years, Flat Island has been an important nesting area for Double-crested Cormorants. Herring Gulls, Common Eiders, and Great Black-backed Gulls nest there as well. The abundance of gulls in recent years is generally lower than numbers observed during the mid 1980s.
Easy access and close proximity to public boat landings contribute to a constant threat of disturbance, especially to the cormorants nesting there. A small beach on the southeastern side of the island further complicates issues of disturbance during the nesting season.
The island is owned by the Maine Dept. of Inland Fisheries and Wildlife and is easily accessible by small boat from several launches including Lincolnville Beach, Bayside, and the ferry terminal on Isleboro. However, this seabird nesting island is closed to human access during the seabird nesting season, April 15 through July 31. During the restricted period, viewing must be from the water only.