Breeding Bird Atlas 2 Species Accounts

American Black Duck


Anas rubripes

  • Somewhat local and strongly declining
  • Conservation action urgent
  • State Wildlife Action Plan listed
“When alarmed [the ducklings] would dive with great celerity several times in succession, but soon became fatigued, made for the shore, ran a few feet from the water, and squatted among the grass, where they were easily caught either by some of our party, or by the Gulls, which are constantly on the look-out for such dainty food.” – John James Audubon, Birds of America

The depredations of human hunters and hungry gulls are but drops in the bucket compared with the challenges faced by American Black Ducks in Massachusetts today. Formerly one of the most widespread and familiar duck species in the Commonwealth, the American Black Duck historically bred from the deltas of the Connecticut River to the tidal marshes of Cape Cod and at many locations in between. The increase of Mallards and the loss of wetland habitat in Massachusetts have combined to make modern life difficult for this once-common native waterfowl species, although, with the scale of the loss in this species it is likely there are more drivers of decline acting on this species.

Historic Status

At one time, hunters and birders in Massachusetts believed they were seeing two separate subspecies of black ducks, Anas rubripes rubripes, the Red-legged (or Winter) Black Duck, and Anas rubripes tristis, the (Summer) Black Duck (Forbush 1925, Phillips 1920). Once the differences between these alleged subspecies were determined to in actuality be sex, age, and possibly even seasonally related rather than pertaining to genetic differences, they were correctly lumped together as representing one and the same species. Regardless of these taxonomic issues, by the 1940s life was becoming increasingly inhospitable for American Black Ducks in Massachusetts. They had successfully survived market gunning for two centuries before other human incursions on their lives set them on a downward trend. Possibly most important was the fact that half of the shallow freshwater marshes existing in Massachusetts in 1951 were lost to development by 1971. Pesticides, urbanization, and further habitat destruction would follow.

Atlas 1 Distribution

Despite these challenges, Atlas 1 found the American Black Duck to be widespread as a breeding species in Massachusetts. The western reaches of the state had fewer occupied blocks than the Connecticut River Valley where fully 50% of the region was hosting breeding American Black Ducks. The birds had greater than 70% block occupancy in the Housatonic Valley. The higher elevations of the Worcester Plateau and the Lower Worcester Plateau also had black ducks present in scattered wetlands, albeit at lower percentages of block occupancy. Concentrations were unquestionably greatest in the east, where they were present in more than 60% of Cape and Islands blocks and in more than half of all blocks in the Coastal Plains, the Bristol/Narragansett Lowlands, and even the thickly settled Boston Basin.

Atlas 2 Distribution and Change

By the time of Atlas 2 American Black Ducks emerged as a species in an unambiguous decline. Losses of breeding black ducks equaled or exceeded gains in every single region across the state. Losses were particularly noticeable in the western river valleys, because both the Housatonic and Connecticut River Valleys reported a disappearance of black ducks from nearly 50% of each ecoregion. American Black Ducks also vanished from 36% (82 blocks) of the Coastal Plains and 44% (44 blocks) of the Bristol/Narragansett Lowlands. Whatever the cause or causes of this alarming decline (hybridization with Mallards, exclusion from high-quality wetlands by Mallards, loss of habitat, and/or hunting pressure) American Black Ducks are sending a clear message.

 

Atlas 1 Map

Atlas 2 Map

Atlas Change Map

 

Ecoregion Data


 Atlas 1Atlas 2Change
Ecoregion# Blocks% Blocks% of Range# Blocks% Blocks% of RangeChange in # BlocksChange in % Blocks
Taconic Mountains531.31.014.00.4-4-26.7
Marble Valleys/Housatonic Valley2871.85.51025.64.2-18-46.2
Berkshire Highlands2952.75.71120.04.6-18-34.0
Lower Berkshire Hills1346.42.6619.42.5-7-25.9
Vermont Piedmont741.21.415.90.4-5-41.7
Berkshire Transition1231.62.4820.03.3-5-16.1
Connecticut River Valley2850.05.5913.83.8-22-45.8
Worcester Plateau2633.35.13742.015.500.0
Lower Worcester Plateau3243.26.31417.55.9-20-37.0
S. New England Coastal Plains and Hills14353.028.16021.225.1-82-36.3
Boston Basin3766.17.31832.17.5-20-36.4
Bristol and Narragansett Lowlands6157.512.01614.06.7-44-43.6
Cape Cod and Islands8764.017.14833.320.1-34-28.3
Statewide Total50852.4100.023923.0100.0-279-33.7
 

Notes

American Black Ducks show a significant declining Breeding Bird Survey trend in Massachusetts and in the New England/Mid-Atlantic Region.