The dominant faunal feature of the island during the summer months is the active Common Tern (Sterna hirundo) colony spread across the flatter areas of the island that are not taken over by bittersweet (Celastrus) or common reed (Phragmites australis).
The other major avian on Great Gull Island is the Roseate Tern (Sterna dougallii), which mostly inhabit the ring of boulders that cover the edges of the island.