Territoriality and the significance of calling in the Lanyu Scops Owl Otuselegans botelensis

Territories of Lanyu Scops Owls Otus elegans botelensis overlap in both bre eding and non-breeding seasons. Results of radiotelemetry showed that neigh bouring owls do not use the shared areas of their territories at the same t ime. Frequent countersinging apparently permitted individuals to avoid pote ntially costly encounters with neighbours. Nonterritorial owls can forage a nd rest in occupied territories. Experiments using decoys and playbacks sho wed that intruding owls were tolerated within either core or peripheral ter ritories in all seasons if they remained silent, while calling intruders al most always incited threats or attacks even in autumn. Tolerating silent ow ls that are not competitors for mates or for nest sites appears to be an en ergy-saving territorial strategy.