The effect of grazing in winter by wild geese on improved grassland in west Scotland.
Abstract
After 2 trials in late winter 1973-4, 6 main experiments were conducted over the winter periods of 1974-5 and 1975-6 to determine the loss of herbage production from improved grassland due to grazing by wild immigrant geese. 3 sites were used: 2 on the Isle of Islay, Inner Hebrides, grazed by barnacle geese (Branta leucopsis) and one near Castle Douglas, Stewartry of Kirkcudbright, grazed by greylag geese (Anser anser). On Islay the potential max. loss of herbage available for spring grazing averaged 1.31 t DM/ha, representing c. 80 cow-grazing days/ha; at Castle Douglas the corresponding loss of herbage averaged 1.51 t DM/ha, representing c. 90 cow-grazing days/ha. Equivalent loss of herbage in silage terms represented an av. of 9 t/ha for Castle Douglas; such quantities represent the silage part of a dairy cow's winter diet. A study of gizzard contents from 20 geese indicated a preference for sown Lolium spp. as opposed to indigenous grass spp. Future management policies for wild geese include control of numbers in the Islay situation and dispersal of geese and the establishment of refuges in the mainland situation.