The importance of the farmland-forest edge for area use of breeding Hooded Crows as revealed by radio telemetry

Abstract

Twenty-six Hooded Crows (Corvus corone cornix) breeding in a fragmented farmland-forest landscape in southeastern Norway were radio-tracked between April and June in three years. The 95% home range size averaged 0.15 km2. The proportional distribution of habitat categories in the home ranges was compared with that in the landscape; EDGE (forest <30 m from open habitats) and FIELD (mainly pastures and gardens) ranked first, followed by CROP (farmland ploughed annually), OLD (forest >30 m from open habitats) and YOUNG (clear-cuts and young planted forest). The same ranking was found when the habitats used were compared with those available within the home ranges. Crows devoted more time to perching, mostly in EDGE, than to foraging, mostly in FIELD and CROP. Use of EDGE increased with increasing availability of EDGE in the home range, but the crows used EDGE more than expected from availability only as long as the proportion of EDGE was <0.40. Home range decreased as the proportion of EDGE in the home range increased. The results suggest that an increase in the farmland-forest edge-to-area ratio may increase the density of breeding Hooded Crows, and thus increase the predation risk on bird nests in edge habitats.