Relating national levels of crop damage to population size indices of large grazing birds: implications for management

1. Populations of large grazing birds have increased in Europe during at least five decades, raising conflicts between conservation and farming interests. Managing these conflicts requires knowledge about the currently unknown relationship between population sizes and crop damage levels. 2. We analyzed unique data on reported, inspected and compensated crop damage caused by geese, swans and cranes together with data from population surveys in Sweden to investigate how bird abundance related to damage levels at the national scale between 2000 and 2015. 3. Over the study period, the annual number of damage reports, yield loss and costs for compensation increased. These crop damage levels were positively related to national population indices of common crane, barnacle and greylag goose. The shape of these relationships varied between species and encompassed considerable uncertainty. However, on a year-to-year basis (detrended data) we found no evident association between damage levels and ...