Territoriality and the significance of calling in the Lanyu Scops Owl Otus elegans botelensis

Abstract

Territories of Lanyu Scops Owls Otus elegans botelensis overlap in both breeding and non-breeding seasons. Results of radiotelemetry showed that neighbouring owls do not use the shared areas of their territories at the same time. Frequent countersinging apparently permitted individuals to avoid potentially costly encounters with neighbours. Nonterritorial owls can forage and rest in occupied territories. Experiments using decoys and playbacks showed that intruding owls were tolerated within either core or peripheral territories in all seasons if they remained silent, while calling intruders almost always incited threats or attacks even in autumn. Tolerating silent owls that are not competitors for mates or for nest sites appears to be an energy-saving territorial strategy. Territoriality is a spacing system maintained by the behavioural patterns of a given species. The reward for territorial defence is frequently better survival or higher reproductive success. The territoriality of a species thus reflects important environmental and social constraints on the species. Models of the external conditions that favour territorial behaviour usually consider the quality, abundance and distribution of