Abstract
During the last two decades, the mid-continent population of lesser snow geese (Anser caerulescens caerulescens), which breeds in the Canadian eastern Arctic, has increased dramatically to at least 3 million birds. In spring, the birds follow the retreating snowline northwards to the breeding grounds. They forage intensively on shoots of sedges just south of the snowline, eating the swollen shoot bases and discarding the remainder. Exclosures were established in 1985/86 at La Pérouse Bay, Manitoba to determine the effects of protection from foraging on the shoot densities of sedges. Between 1986 and 1995, numbers of shoots increased from 1.1 to 2.2 times in exclosed plots, while numbers in grazed plots declined to between 0.19 and 0.33 times their original values. Sedge assemblages were replaced by moss carpets or standing water rich in peat debris. The ecological significance of the results is discussed in relation to re-establishment of vegetation and the role of herbivores in changing species assemblages.