Vocal duets in a nonpasserine: an examination of territory defence and neighbour-stranger discrimination in a neighbourhood of barred owls

Mated pairs of animals in many taxa coordinate their vocalizations into duets, yet most research on duetting has focused on songbirds. Here we examine the duetting behaviour of barred owls (Strix varia) by addressing three questions: (1) Do owl duets play a role in territorial interactions? (2) Do owls discriminate between duets of neighbours versus strangers? (3) Do duets play a role in extended communication among a neighbourhood of owls? We simulated territorial encounters by broadcasting duets of adjacent, territory-holding owls (neighbours) and distant owls (strangers). We assessed responses to playback using a 3.5-km transect of automated recording devices. We compared vocal activity during a pre-playback period and following both playback treatments for the focal pair, their neighbours, and more distant owls within the neighbourhood. After playback, focal owls gave significantly more duets, vocalized for a longer duration, and emphasized different call types compared to the pre-playback period, demonstrating that barred owls use duets in territory defence. Focal owls did not respond significantly differently to neighbours versus strangers. At the neighbourhood level, owls did not behave differently during silent pre-playback periods or post-playback periods. Our results suggest barred owl duets function primarily in immediate confrontations during territorial conflicts.