Predicting autumn population sizes of tetraonid game birds from reproduction data of pied flycatcher Ficedula hypoleuca Original Research Article

Data on the breeding success of the pied flycatcher, which reflects the combined effects of various biotic and abiotic factors affecting the quality of the breeding habitat each year, could explain more than three quarters of the variation in the autumn population levels of woodland tetraonids (capercaillie Tetrao urogallus and black grouse T. tetrix) in a subalpine forest area in Lierne, central Norway, during the period 1986–1995. The applicability of a simple regression model is evaluated on the basis of the data from 1996. Much less time is required to collect these breeding parameters on the flycatcher from nest boxes than to obtain reasonably good population estimates for the tetraonid species themselves directly. Data on the production of pied flycatcher, collected well in advance of the shooting season, could be used to set bag limits for woodland tetraonids the following autumn. This might be used as a tool for sustainable harvest to avoid future over-exploitation of these species in years with predicted low production.