The southern two-thirds of Plum Island make up one of the most important migratory bird refuges on the Atlantic flyway — over 300 species recorded, including snowy owls in winter, godwits and dowitchers in the salt-pannes, and the swallow roosts in late summer. Hawk migration peaks in September.
A six-mile road runs the length of the refuge with seven beach-access parking lots; boardwalks lead from the lots over the dunes to the surf. In summer the beach is closed to walking south of lot 3 to protect nesting piping plovers and least terns — a sign of the refuge taking its job seriously. Admission is by vehicle pass; arrive early on summer weekends, when the gates close once the lots fill.