Destruction of wetland habitats by lesser snow geese: a keystone species on the west coast of Hudson Bay.
The numbers and distribution of lesser snow-geese (Chen caerulescens) and their effects on plant communities were studied in a 40 × 200 km area roughly centred on Eskimo Point. Patterns of foraging varied in space and time. In spring at the nesting sites, before the onset of aboveground vegetation growth, adult geese grubbed for roots and rhizomes of graminoid plants in relatively dry areas, and in wet habitats they ate the swollen bases of shoots of sedges, particularly Carex aquatillis. In summer, adults and goslings grazed intensively on leaves of grasses and sedges over wide areas. Swards dominated by Carex subspathacea were produced in brackish marshes, but the leaves of graminoids of the freshwater sedge meadows were also clipped extensively. Grubbing of vegetation by geese each spring creates bare areas (1-5 m2) of peat and sediment. The increased numbers of birds have increased the scale of disturbance, with large areas now stripped of vegetation, particularly by the McConnell River. At some sites, erosion of peat has exposed the underlying glacial gravels. It is unlikely that the vegetation which re-establishes will closely resemble the original. Further expansion of goose colonies in this region may be limited by available food resources.