The impact of wild geese visiting improved grasslands in the Netherlands.
The number of migratory geese spending winter and early spring in the Netherlands increased from 100 000 in the early 1960s to almost 600 000 in the 1983-84 winter. The most common geese species were Anser albifrons, A. anser, A. fabalis, A. brachyrhynchus, Branta leucopsis and B. bernicla. Their increase was accompanied by a growing number of complaints by dairy farmers about yield losses and deterioration of their swards. The yearly amount paid by the Dutch government to protect the geese and compensate farmers rose from #1500 in 1974 to #450 000 in 1984. In order to establish an objective method for the assessment of damage, a combination of grazing, treading and defaecating by wild geese on Lolium swards was studied in the province of Friesland. Grazing by wild geese on improved grasslands in winter and early spring resulted in DM yield losses at first cut or grazing of 335-1100 kg/ha depending on grazing pressure, time of grazing and productivity of the sward. There were no yield losses after the first cut. There were no significant effects of goose grazing on the number of plant species in a sward nor on the number of tillers/dm2 per plant species. The significant increase in net energy value of spring pasture as a result of goose grazing did not compensate for the loss of herbage production. Defaecating and treading by wild geese had no demonstrable effect on chemical or physical soil characteristics such as N, P, and K contents of the upper soil layer, water conductivity and compaction. Since the retardation of growth of grass in spring resulting from goose grazing usually takes place on paddocks that are mown instead of being grazed by livestock, it is discussed whether a farmer could counteract the effects of goose grazing by means of small adaptations in the grassland utilization scheme.