The ecology and mortality of swans at the Ouse Washes, England

摘要: The ecology and feeding behaviour of Mute Cygnus olor, Whooper C. cygnus Bewick's Swans columbianus bewickii over six winters 1969-1975 at the Ouse Washes, England, is described. An analysis made winter mortality swans site. exploited three distinct food sources during period: natural vegetation on washes, grain which was specially provided crops, particularly waste potatoes, adjoining farmland. When meadows, preferred soft grasses, Agrostis stolonifera, Alopecurus geniculatus Glyceria fluitans, to coarser species also available. maxima was, however, an important late food. starchy roots Rorippa palustre were a prominent constituent in diet first two after plant decreased. Seeds wetland plants animal material insignificant contribution diet. Once supplementary with started large proportion use it. Since 1972-1973 many have fed neighbouring fenland farms. It suggested that change brought about by increase swan usage following creation undisturbed refuge, possibly birds searching for high-energy foods replace declining Rorippa. Undisturbed water increased their activity day continued feed dark. By contrast, when farmland intensively morning later afternoon period relatively low midday. On average 3% Swan population 1.4% Washes died each winter. Collisions power lines (30%), poisoning from ingested lead pellets fishing weights (29%) shooting (8%) accounted most deaths 128 recorded winters. Birds are likely ingest as grit this deficient area provision areas or roost might lessen poisoning. Although changes probably beneficial birds' nutrition, grain-feeding increases susceptibility death flighting farms collisions lines.