Responses of hayfield vegetation to spring grazing by greater snow geese.
Field studies at Montmagny, Quebec showed that the use of hayfields (dominated by Medicago sativa, Trifolium pratense, Phleum pratense, Agropyron repens, Festuca rubra and Poa pratense) by greater snow geese (Chen [Anser] caerulescens atlantica) more than tripled between 1980 and 1985. The total seasonal quantity of droppings increased from 7.0 to 22.6 droppings/m2. Over the same period, the mean decrease in total harvestable biomass at 1st harvest almost doubled (from 47 to 78 g/m2) and made up 25% of the potential yield. The proportion of cultivated and wild grasses decreased with grazing by geese and decreased from 1980 to 1985 while the proportion of legume and weed species increased. These changes were greater in new than in old hayfields. It was concluded that the combination of rapid increases in goose population and decreases in hayfield area in Montmagny will soon give unacceptable grazing pressure levels.