Winter habitat use of New Zealand falcons (Falco novaeseelandiae ferox) in an intensively managed pine plantation, central North Island, New Zealand

摘要

Deforestation and conversion to intensive agriculture historically caused a large reduction in abundance of the New Zealand falcon, resulting in its current classification as At Risk. Many New Zealand falcons occur in managed plantation forests, but little is known about their winter use of the mosaic of different aged stands present in these forests. We radio tracked adult falcons (n = 36) during three winters (2012-2014) in Kaingaroa Forest, an intensively managed pine plantation located in the Central Plateau of the North Island of New Zealand. We used tracking data to establish the extent and habitat composition of winter home ranges, and transect surveys to assess the availability of potential prey (passerine birds). We also investigated whether falcon habitat use was related to weather. Open fields created by clearcutting were the primary hunting ground of falcons. Falcons occupied young pine stands (30.4) and the ecotone between young and mature pine stands (31.2) most frequently despite its limited availability (20.1 and 3.7, respectively). Total prey abundance was similar across all habitats and sizes of open fields, but the species composition of potential prey differed significantly between habitats. Thus, the dynamic changes to forest structure created by clearcutting and its effects on prey accessibility are the most important factors influencing falcon space use. We observed that falcons used the mature portion of the forest edge area as a vantage point for hunting or for territorial defence and as a shelter from heavy rain, and interiors of mature tree stands as a shelter from strong winds. Females had a larger home range size (95 KDE, 32 km(2)) than males (15 km(2)). The availability of mature/young edge within a home range may be the key factor determining home rangesize during winter. Maintaining the availability of ecotones of young stands adjacent to mature trees in plantation forests can assist in supporting falcon populations in this novel habitat and hence the conservation of this endemic raptor.