The refuge contains 4,662 acres of sandy beach and dunes, bogs, freshwater impoundments and tidal marshes. The following list, which conforms to the Sixth American Ornithologists' Union Checklist, contains 302 species that have been recorded on or seen from the refuge during the past 20 years. A separate list is included of 39 species that have been seen several times during this period. This list was prepared in cooperation with the Massachusetts Audubon Society, the Brookline Bird Club, the Peabody Museum, and numerous knowledgeable local birders. Bird activity on the refuge is highlighted by shorebird migrations and flocks of swallows in late summer and large flocks of waterfowl in the fall and early spring.
Most birds are migratory.
The peak migration periods at Parker River are usually March 1 to June 7, and August 1 to October 31. The National Wildlife Refuge System is a network of lands and waters managed specifically for the protection of wildlife and wildlife habitat and represents the most comprehensive wildlife resource management program in the world. Units of the system stretch across the United States from northern Alaska to the Florida Keys, and include small islands in the Caribbean and South Pacific. The character of the refuges is as diverse as the nation itself. The Service also manages National Fish Hatcheries, and provides Federal leadership in habitat protection, fish and wildlife research, technical assistance and the conservation and protection of migratory birds, certain marine mammals and threatened and endangered species.