Influence of prey availability on re-establishment of Goshawk Accipiter gentilis nesting territories

Abstract

Despite many years of protection, nesting Goshawks (Accipiter gentilis) are still killed by man in Norway to save small game, especially grouse, from predation. In a 650-km2 area in southern Norway, the re-establishment of Goshawk nesting territories was studied during four, 4-year periods 1972-75, 1980-83, 1984-87 and 1988-91. After a reduction in the Red Fox (Vulpes vulpes) population because of an infestation of sarcoptic mange, the grouse population increased during 1984-87, and then remained high for the rest of the study period. The number of Goshawk nesting territories per 100 km2 was three/year in 1972-75 and in 1980-83, and four/year in 1988-91. During these periods, the nesting territories were regularly spaced, and their number and distribution were unaffected by the removal of breeding birds. During 1984-87, five nesting territories, in which one or both of the breeding hawks had been removed by man, were replaced by eleven new ones. The study results indicate that removal of breeding pairs of goshawks may lead to an increase in the breeding density during periods of increasing food availability.