Large grazing birds and crop damage : investigating spatial and temporal patterns to guide management practices

Populations of geese, swans and cranes (i.e., large grazing birds) are increasing in Europe and North America, raising conflicts between conservation and farming interests when, foraging in agricultural fields (often in the vicinity of wetlands), cause yield loss for farmers. The aim of this thesis is to increase the understanding of spatial and temporal patterns of large grazing birds and their crop damage to improve future management practices. At the national level, crop damage was found to be positively related to national estimates of bird abundance. At the regional level, crop damage followed seasonal patterns associated with vulnerable stages of crops and the crop selection by the culprit species. Seasonal patterns remained consistent over the years but differed across the country, relating to the spatial distribution of different crops and culprit species. Large grazing birds showed a clustered spatial distribution across the country with distinct hotspots of high abundance. The spatial variation in abundance of large grazing birds were largely reflected in a corresponding spatial pattern of crop damage as reported by farmers. The complexity of the system (e.g., weather dependence, opportunistic behaviour of the birds) and the coarse temporal and spatial resolution of the available data probably caused model predictions of crop damage to be characterized by large uncertainties. My results suggest that it is necessary to integrate management strategies across different spatial and temporal scales when implementing current and future management actions for crop damage prevention.