Interactive effects of climate and forest canopy cover on Goshawk productivity

Abstract

In the current scenario of human-induced environmental changes, boreal forest biodiversity appears to be threatened by both deforestation for timber production and climate change. A northern species which has experienced a decline due to ongoing habitat degradation in Finland is the Northern Goshawk (Accipiter gentilis), a forest-dwelling avian predator that inhabits mostly mature coniferous forests. In order to uncover possible interactive effects of climate and landscape structure on this species, we tested whether temperature and precipitation affect Goshawk reproductive performance differentially in closed (i.e. forest) or open (mainly forest–farmland mosaics) habitats, accounting for land cover at different distances from nests (250, 500, 1000 and 2500 m). Long-term data on brood size and individual chick weight were used to describe breeding success over an 18 year period. Brood size was negatively associated with March and May temperature and positively with June temperature, but no trends related to landscape structure were identified. Chick body condition was negatively affected by high forest cover closest to the nest (250 m), but negative effects of June precipitation on this variable proved to be significantly greater in open than in closed habitats, with results consistent at different scales, i.e. precipitation had greater negative effects on chick body condition in open than in closed landscapes. Precipitation is forecast to increase in the region as a result of climate change, hence forest cover could exert a positive role in mitigating adverse effects of unfavorable climatic conditions. Outcomes of this study may be used to inform sustainable timber harvest management strategies.