| Summary: | Human-caused habitat changes have led to declines of many species by impairing their occurrence, reproduction and interactions with other species. In Northern Europe, intensive forestry has transformed boreal forests and worsened conditions of species dependent on old forest, but the mechanisms by which habitat changes affect species are often unknown. In my dissertation, I examined habitat changes, their effects and habitat-associated breeding performances of three declining forest-dwelling hawks, the northern goshawk (Accipiter gentilis), the common buzzard (Buteo buteo) and the honey buzzard (Pernis apivorus). These species can compete for nest sites and goshawks can also predate the buzzards. Raptors may lack nest sites in managed forests which is why their nesting has been supported by constructing artificial nests. I analysed the breeding success of the hawks in artificial nests since their benefits as a conservation measure were not previously analysed. Finally, I studied the conditions when dominant species can exclude subordinate ones in competition for suitable nest sites. According to my results, old forests have decreased and young forests increased throughout southern Finland. These changes are adverse for the goshawk whose breeding success improves when old spruce forests are more abundant and young forests scarce around their nests. Breeding performances of the common buzzard and honey buzzard were not significantly associated with habitats. However, common buzzards were reluctant to re-occupy nests surrounded by a vastness of old forest. The breeding success of the goshawk and common buzzard was lower in artificial nests than in natural ones. Thus, this measure aimed at enabling hawk breeding in managed forests seems to conflict with its conservation objectives. I discuss the possible contributing factors and directions for further investigations. Interspecific interactions with other raptors proved to be important when a subordinate hawk decided on territory occupancy. Common buzzards prefer to ...
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