You are here:
HABITAT RELATIONSHIPS OF WATERFOWL WINTERING IN NARRAGANSTT BAY
Citation:
McKinney, R A. HABITAT RELATIONSHIPS OF WATERFOWL WINTERING IN NARRAGANSTT BAY. The Rhode Island Naturalist . Rhode Island Natural History Survey, Kingston, RI, November:3-6, (2004).
Description:
Coastal marine habitats often provide essential structure and life support functions for estuarine-dependent wildlife such as wading birds, small mammals, and waterfowl. Unfortunately, these areas are increasingly being lost or degraded by watershed development and human disturbance. We are trying to determine how changes in habitat quality brought about by habitat loss or impairment affect resident wildlife species by conducting a study of patterns of habitat utilization by wintering waterfowl in Narragansett Bay. Starting in 2001, we conducted periodic surveys to determine which waterfowl species use the Bay in winter, and to identify specific habitats that support different species. A total of 17 species of waterfowl inhabit the Bay in substantial numbers, including 10 species of sea ducks, 4 species of dabbling ducks, Canada geese, brant, and mute swans. For several years, we have also conducted bimonthly censuses at 12 study sites located along a gradient of human disturbance. We analyzed data from these sites using abundance weighted principal component analysis (AWPCA), an exploratory multivariate statistical technique, to investigate habitat and landscape characteristics influencing patterns of utilization by waterfowl. Fifteen habitat characteristics were reduced to two principal components that accounted for 67.9% of the variance amongst sites. Principal component axes described characteristics such as vegetation or salt marsh within a 100 m buffer around the site, residential development, and forested or man-made buffer from wind. When species were plotted from weighted averages of the principal component values of the sites where they were found, two distinct groupings of species and habitats were apparent: rocky headland sites and species located near the mouth of the Bay, and shallow, salt marsh dominated cove sites and species. Visual analysis of an AWPCA plot of the rocky headland sites and species revealed that waterfowl tended to avoid sites with adjacent residential development in favor of sites with high area of vegetation or salt marsh in a 100 mm radius around the habitat and high forested buffer that may provide protection from prevailing winds. An AWPCA plot of the salt marsh dominated cove sites and species revealed no clear patterns other than a tendency, particularly for dabbling ducks and Canada geese, towards favoring sites with higher amounts of adjacent forested land or structures that could potentially block prevailing winds and higher residential development in a 100 mm radius around the habitat. We also used AWPCA to look at the influence of prey abundance and prey species diversity at the sites on waterfowl utilization, but saw no clear patterns other than a tendency towards favoring sites with high abundance of gastropods. Although exploratory in nature, AWPCA provides information about habitat and landscape characteristics that may be influencing habitat utilization by wintering waterfowl in Narragansett Bay. From our analysis, we concluded that adjacent forested land or man-made structures that could potentially block prevailing winds, salt marsh area, and residential development are important habitat characteristics that should be considered in future, more rigorous modeling efforts.