Spacing of birds of prey in southern Finland

Abstract

Birds of prey were studied in central Uusimaa, southern Finland, during 1972-90. Eight diurnal species and six owl species bred regularly in the study area (of up to 4800 km2). As their food supply was relatively stable, most long-term territorial (site- tenacious) species demonstrated even spacing of nesting places, while irregular pat- terns characterized the widely fluctuating short-term territorial (nomadic) vole specialists. Dispersion of traditional nesting places had a major effect on spacing of occupied locations. Irregularities in spacing of nesting places were largely due to the uneven distribution of suitable habitats . Avoidance of predation might have affected the spatial structure of the bird assemblage studied, while interspecific competitive effects were less evident.