Correlates of hoot rate and structure in male Tawny Owls Strix aluco: implications for male rivalry and female mate choice

The patterned hooting of owls may serve one or more functions including repulsion of territorial invaders, attraction of potential mates, and stimulation of the mate. In this study I looked For characteristics in the Tawny Owl hoot which might convey information on the signaller's quality or that of its territory to potential mates and rivals. I therefore analysed relationships between hooting rate, hoot harshness and 13 structural features of the hoots of 22 territory-defending male Tawny Owls on the one hand, and male RHP (i.e., aggressiveness in response to playback), territory size, stability, patchiness, fragmentation and owl reproductive output on each territory on the other. Hooting rate, hoot harshness and rhythm were all related to male RHP, but not to any measure of territory quality. These features therefore appeared to reflect aspects of male competitive potential, i.e. the male's quality as a defender. By contrast, duration and frequency range of notes were related to reproductive output and territory stability, possibly signalling better territories in terms of resources and better male parental performance. Males involved in territorial contests increased their hooting rate when females joined them in a communal response. This more conspicuous display, rather than functioning as a mate guarding strategy, may be interpreted as a means of influencing female choice directly.