Oyster Bay has the greatest winter waterfowl use of any of the Long Island national wildlife refuges. The numbers of waterfowl using Oyster Bay are lowest from May through August, and start to increase in September and October. Puddle ducks such as black ducks, gadwall, and mallards start migrating to the refuge in early autumn, and their diversity begins to increase in November. Waterfowl numbers peak and remain high from December through March, then decline in April.
The New York Department of State has singled out Oyster Bay as having the greatest concentration of waterfowl on Long Island’s north shore.
The three waterfowl species that most commonly use the refuge in winter include the greater scaup, bufflehead, and black duck. Those species compose approximately 85 percent of all ducks using the refuge. Greater scaup compose more than half; bufflehead make up 20 percent; and black duck, the most common puddle duck species, close to 10 percent.
Waterfowl use is not uniform across the refuge. The Bayville, Cold Spring Harbor, and Mill Neck Creek areas support in excess of 80 percent of that use. Bayville alone accounts for nearly half. The majority of the greater scaup and bufflehead on the refuge use its Bayville and Cold Spring Harbor sections, while the Mill Neck Creek section had the greatest use by black duck and canvasback.