2.2. Collection of food remains and breeding data

Food remains have been collected from 38 different goshawk nesting sites since 1965 in Oulu district. The total material contains some 4341 prey specimens. From 1965 to 1988 collection was fairly sporadic, then it became more systematic. Material collected from the surroundings was separated from that found in the nests. During the breeding season prey remains can be found outside the nest during the incubation period but also during the fledging period when goshawk broods forage near the nest for about one month after fledging (Sulkava 1964, Huhtala 1976, Kenward et al. 1993). From 1988 to 1994 collection was done at two week intervals to get a more detailed understanding of the prey choice during the breeding season. Breeding status of all known nesting territories was checked in the course of the collection of food remains. Nests without any signs of new building were considered unoccupied. Nests ‘decorated’ with fresh twigs were classified as occupied. In all successful nests, the nestlings were weighed, wing length measured and ringed. In most cases the eggs were also counted and measured. In some cases, successful nesting wasn’t noticed until the fledging period when noisy chicks revealed the nesting site.