Differential response of territorial Tawny owls (Strix aluco) to the hooting of neighbours and strangers

Male Tawny Owls Strix aluco have individually distinct hooting calls. A classic play-back experimental design was used to examine the differences in behavioural responses of a known owl to the hooting of a neighbour (familiar) compared with a stranger (unfamiliar) in order to test the hypothesis that such hooting variations are used in calibrating interactions between conspecifics. We tested 12 male Tawny Owls and their mates; the overall intensity of agonistic response was significantly higher when we stimulated birds using playbacks of strangers than when we did so with those of neighbours. The behaviour displayed and the type of voice used by Tawny Owls were stronger toward strange males. Moreover, on the occasions we broadcast a strange male hooting, the singing rate was higher while the latency was lower.