This shrub and forb-dominated island is one of the most exposed islands in Casco Bay and is characterized by steep rocky bluffs and deep surrounding waters.
In recent years, a breeding tern colony has been restored to the island through the efforts of National Audubon. With restoration, the breeding colony has swelled to nearly 1,000 nesting pairs of Common Terns. This island is also an important nesting island for Double-crested Cormorants, Common Eiders; over 92 species of migratory songbirds have been documented on this island in the past few years alone.
Given the remoteness of this island, it is especially valuable as a safe harbor for the terns, as other islands closer to the mainland have recently experienced predation by both birds and mammals. The greatest threat to this island probably would be an oil spill.
Outer Green Island is owned by the Maine Dept. of Inland Fisheries and Wildlife and landing on this seabird nesting island is prohibited during the nesting season (April 15 ? July 31).