"This is a prime site for a variety of seabirds, especially those that spend winters off the Maine coast. Common species include cormorants, Long-tailed Duck, and Common Eider. Occasionally King Eider show up here. Other ducks include American Black Duck, Bufflehead, Gadwall, Common Goldeneye, and Whitewinged Scoter. Marginal Way is famous for its population of Harlequin Duck. The Maine Department of Inland Fisheries and Wildlife (DIF&W) listed Harlequin Duck as threatened in 1997.
As of 2006 DIF&W estimated the eastern North American population of harlequins at somewhere between 1,800 and 2,000 individuals. Of these, about 1,300 spend the winter in Maine. Harlequins are seldom seen because they spend much of their time on the barren shores of Maine’s offshore islands. However, several flocks spend the winter off Ogunquit, and these are what visitors to Marginal Way see. A visit here is by far the easiest way to see Harlequin Duck. Also present are Common and Red-throated Loon, Ring-billed Gull, Black Guillemot, Herring Gull, Great Black-backed Gull, American Crow, and Fish Crow."