Spatial behaviour of little owls (Athene noctua) in a declining low-density population in Denmark

Abstract

Knowledge of a species’ spatial behaviour is essential for understanding its behavioural ecology, as well as a prerequisite to planning of conservation strategies. The Little Owl (Athene noctua) has shown a substantial decline in north-western Europe and is on the road of extinction in Denmark. To quantify relevant aspects of spatial behaviour in the last remaining Danish population, we followed 27 radio-tagged owls representing 14 territories during a period of 2 years. Mated owls were resident at nesting sites year-round with half of all nocturnal locations found within 125 m. Mean nightly distance from roosts peaked in January at 249 m (95% CI = 195–319) and dipped in May to 89 m (66–121). Distance from roosts varied non-linearly with temperature with the longest distances found at 6°C. Home range size varied with more than a tenfold difference between pairs, with pairs with neighbours maintaining 2–3 times larger ranges than isolated pairs independent of habitat composition. Mean home range size of 14 pairs was 41 (95% CI 27–64) and 2.6 ha (1.5–4.5) for 90 and 50% minimum convex polygons, respectively. Males and females behaved similarly, except in the breeding season where females foraged closer to the nest. Mates overlapped completely in activity distributions and were located closer to each other than expected by chance, suggesting a permanent pair-bond. Inter-mate distances were not shorter prior to egg laying compared to the rest of the year, indicating little male investment in mate guarding. No mates left their partner, but widowed birds left their territory within 6–12 months if unable to attract a new mate.