Waterfowl species flock to our coastal systems in huge numbers during migration season (late fall and winter), when freshwater areas freeze. Estuaries and coastal ponds are saline and freeze more slowly, if at all, making them an important food resource to waterfowl when ice and snow cover the landscape. Coastal wetlands have also been under siege from human activity and therefore are a conservation target.
American Black Ducks (Anas rubripes) have historically bred in Massachusetts but have suffered declines due in part to wetland loss, are of longstanding value to the hunting community, and are highly dependent upon estuaries in winter. For these reasons black ducks are an important target species for research and conservation in their winter range. Allens Pond estuary is a system studied extensively by the Lloyd Center due to its high abundance and diversity of waterbirds, and is used extensively by migrant black ducks.
Starting in December of 1988, the Lloyd Center began using waterbird surveys of Allens Pond to assess the importance of the system to black ducks in winter. Over time, this survey evolved into a regional assessment of waterfowl, utilizing systems from the Sakonnet River in Rhode Island to Apponagansett Bay in Dartmouth. As of February 2022, the “Annual Lloyd Center Waterfowl Count” reached its 35-year milestone. In addition to providing insight as to use of these systems, surveys of migrant waterfowl are also an indicator of population levels for various species that arrive here from breeding ranges.
Each season, an early December (early meteorological winter) and a late January or early February survey (late meteorological winter) is conducted, the two surveys accounting for differences in both migration schedules of species and ice coverage that is based upon weather patterns, but trends higher in late winter. On the two Sundays, volunteers identify and count all individuals present at their respective sites, and estimate percentage of ice coverage, given that ice coverage determines waterfowl abundance at sites.
Groups of waterfowl studied include geese, swans, dabblers (ducks feeding from surface) and divers (ducks diving beneath surface). Dominant species include the familiar Canada goose (Branta canadensis) and Mallard (Anas platyrhynchos), both common in parks, fields, and at human feeding stations, thus reducing their numbers in coastal systems. However, winter ice formation and snow cover forces these adaptable species to the coastline and both species in winter include local and more migratory birds.
American Black Ducks (Anas rubripes) have suffered from competition with Mallards, but the large population that depends upon estuaries are mainly migrants from the north. Two dominant divers are bufflehead (Bucephala albeola), and red-breasted merganser (Mergus serrator), each of which consume invertebrates, fish, or vegetation, and like the black duck, rely more exclusively on these systems.
The aerial photo (Figure 1) and accompanying table (Table 1) depict site locations and dimensions, along with summaries of ice, estimates for the initial 25-year study (currently being updated). The summary of waterfowl numbers depicts dominance trends of the above-mentioned species and others for each month separately and the waterfowl season as a whole, over this same 25-year period.