During any given summer season, over 100 species of birds are observed by researchers on the island.

It is home to colonies of many types of seabirds, including Atlantic puffins, double-crested cormorants, razorbills, Leach's storm petrels, eiders, and black guillemots.

Seal Island is the last refuge for the dwindling great cormorant population in the Gulf of Maine, with 35 pairs in 2018.

During the Cold War, the island was used as a gunnery range and bombing test site for the United States Navy.

This article incorporates public domain material from websites or documents of the United States Fish and Wildlife Service.