1.2. Long-term change in the diet of the goshawk

Grouse, as a stable food source for goshawks, have dramatically decreased in Finland since the start of grouse censuses in the beginning of the 1960’s. (Linden & Rajala 1981). However, the goshawk population has not decreased by the same amount, as would be expected, based on the central importance of grouse in the goshawk’s diet (Saurola 1985, Haapala et al. 1994, Väisänen et al. 1996). On the other hand, changing forests might have created new sources of food. At least the vole has benefited from clear-cutting, which increases the growth of grasses and bushes; the favourite food of field voles (Larsson & Hansson 1977, Henttonen 1989), and possibly also of hares. The continual rise in man’s standard of living produces more waste, utilised by corvid birds and rats, which are suitable food for raptors and owls. The number of corvids has markedly increased since the 1950s, in particular, in the last two decades (Väisänen et al. 1996). Therefore, one can ask if these potential alternative prey types have been sufficient to make up for the lack of grouse in the goshawk’s diet.