Are common bird monitoring schemes and opportunistic observations appropriate for estimating raptor trends

ABSTRACTCapsule: Transect-based common bird monitoring methods and opportunistic data from citizen scientists are not equal alternatives to mapping of raptors in study plots.Aims: To analyse the efficacy of common breeding and wintering bird monitoring schemes, as well as databases of casual bird observations, in providing population trends for raptors.Methods: We estimated trends for three raptor species using data from Estonian common bird monitoring schemes and a database of casual observations, and compared these with those resulting from special raptor monitoring programmes.Results: Significant trends for all three species were only detected using the specialized scheme Monitoring of Breeding Raptors in study plots, whereas Monitoring of Wintering Raptors showed some significant yearly fluctuations of the Common Buzzard Buteo buteo. However, Common Breeding and Wintering Bird Monitoring schemes provided uncertain trends, although results suggested a decline in the breeding Goshawk Accipiter gentilis ...