Showing papers by "Royal Society for the Protection of Birds published in 1982"

Autumn and winter feeding ecology of waterfowl at the Ouse Washes, England

Abstract: The potential foods available to waterfowl at the Ouse Washes in autumn and winter are described. All were commonly found in the river, pool, marsh and flooded grassland habitats of the washes and in the surrounding arable fields. Gadwall Anas strepera, Wigeon A. penelope, Moorhen Gallinula chloropusand Coot Fulica atramainly consumed vegetative foods, especially the leaves of grasses and in the case of the first named, water plants. Mallard A. platyrhynchos, Pintail A. acuta, Teal A. crecca, Pochard Aythya ferinaand Moorhen fed extensively on fruits and seeds with the first three species supplementing their diets with cereal grains from stubbles. Shoveler A. clypeata, Tufted duck Aythya fuligula, Pochard and Moorhen consumed the largest amounts of invertebrates. Within these three groupings there were further interspecific differences in diet. With most species diets also differed under low and high floods, being most similar under the latter. Amongst the dabbling ducks Anasspp. there were differences, probably minor, in foods taken attributable to differences in the bill lamellae on the outer margins of the upper jaw. The feeding methods used under low and high floods are described and some differences may further serve to ecologically separate the waterfowl. There was a high degree of adaptability, especially amongst the dabbling ducks, with some species changing the feeding postures completely under high floods. All species fed diurnally. Wigeon, Gadwall, Coot and Moorhen all fed for at least 90% of the daylight hours. Shoveler, Teal, Mallard and Pintail were most active in the mornings and afternoons. A partially objective analysis of ecological niches shows that all but two species pairs were clearly separated by either habitat or food factors. There is some overlap between Pochard and Tufted duck and greater overlap between Mallard and Pintail. This may be because they are utilizing the temporarily abundant foods present at this site.