Survival, ranging, habitat choice and diet of the Northern Goshawk Accipiter gentilis during winter in Northern Finland

Abstract

The winter ecology of the Northern Goshawk Accipiter gentilis was studied in northern Finland in 1991‐95. The data consist of 26 radiomarked hawks, of which 331 day and 299 night positions were located. Average range size was 9894 ha for males (minimum convex polygon, n= 4) and 6282 ha for females (n= 11). Ranges calculated by the 75% harmonic mean contour gave range areas of 3283 ha for males (n= 3) and 2753 ha for females (n= 11). Harmonic mean centres concentrated near human settlements, implying better food availability there compared with woodland areas. Some Goshawks preyed upon animals living in the city dump in late winter. Goshawks preferred deciduous and mature conifer forests and avoided open areas such as fields and bogs. They also avoided very heterogeneous sites. The winter diet consisted mostly of Mountain Hares Lepus timidus (30.9%), Red Squirrels Sciurus vulgaris (23.6%), Brown Rats Rattus norvegicus (12.7%) and forest grouse Tetraonidae (27.1%), of which Black Grouse Tetrao tetrix was the most important (14.5%). By weight, hares constituted 70% of the biomass consumed.