By Kurt Anderson and John Coluccy, Ph.D.
are the iconic waterfowl of the Atlantic Flyway
. Once more numerous than mallards throughout this flyway, black ducks still migrate and winter in impressive numbers on the vast salt marshes that buffer the Atlantic Ocean and Chesapeake and Delaware bays. Black ducks are hardy and difficult to hunt. Especially wary of human presence, they have fooled and frustrated waterfowlers ever since the first English colonists settled at Jamestown. Among waterfowl, no other species is more revered by those who hunt them.
Sadly, population estimates suggest that black ducks have experienced a steady decline since the 1950s. In 1986, the North American Waterfowl Management Plan (NAWMP)
established a population goal of 385,000 wintering black ducks. While the birds have shown recent increases on their breeding grounds, black duck numbers remain nearly 30 percent below the NAWMP goal. Several explanations for this have been proposed, chief among them overharvest, hybridization with mallards, habitat loss, and disease, but population models have failed to identify a single factor driving the black duck's decline.
Enter Ducks Unlimited. DU has launched a multiyear initiative to address the decline of black duck populations, including an extensive study using satellite tracking technology to learn more about the birds' migration habits. DU researchers captured 68 adult female black ducks during the winters of 2007–2008 and 2008–2009 in Delaware, New Jersey, New York, Ohio, and Virginia. These birds were outfitted with solar-powered satellite transmitters that were programmed to provide six GPS “fixes” each day. This data enabled researchers to track the birds' migration routes, identify major migratory stopovers, and examine habitat use.
DU researchers captured and attached satellite transmitters on hen black ducks before releasing them. (photo by John Coluccy, DU)
The single most important migration route for black ducks extends along the Atlantic coast from eastern Canada to Virginia. This corridor is followed by more than 50 percent of black ducks wintering in New Jersey, as well as a large proportion of black ducks that winter on the Delmarva Peninsula. Nine black ducks carrying satellite transmitters followed this route during the spring migration. The Hudson River Valley and St. Lawrence River are also used by migrating black ducks, and 10 birds in the DU study followed either one or both of these routes. Another important migration route extends from Ontario and western Quebec through New York to Chesapeake Bay. Most black ducks harvested along the western shore of Chesapeake Bay follow this migration corridor, and so did three black ducks carrying satellite transmitters in this study.