Characteristics of cliff nest sites of Golden Eagles in forested hills of southeast Norway

Abstract

Cover photo: Adult Golden Eagle. Photo: Kristian Henriksen. The characteristics of cliff nest sites of the Golden Eagle Aquila chrysaetos were evaluated from a sample of 57 nests, located during 2000–2020 in the forested valley of Valdres in southeast Norway. About 80% of nests were facing to the south and east, but availability of nest ledges seemed largely a consequence of cliff structure and orientation. Among the 57 nest sites, 4% were placed in a corner with vertical walls, 33% on a ledge with overhang, 10% on a ledge with a vertical back wall, 2% on a ledge with a reclining wall, 49% within a cavity and 2% within a cave. Thus, about 83% of the nest sites were sheltered by an overhang, a cavity or a cave in the cliff within 0.5–2 meters from the nest, and only 16% of sites lacked shelter from above. Heavy snowfall in early spring, torrential rain or strong winds in spring and summer may increase mortality among the nestlings unless the nest site is well sheltered. Moreover, a dry and snowless nest may allow the eagles to start early incubation in late March, thereby increasing fledgling survival. Cavitynests are sheltered sites with less visibility that might protect from attacks from other raptors and Ravens Corax corax.