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Tawny owl vocal activity is constrained by predation risk

Authors


R. Lourenço, Dept of Conservation Biology, Doñana Biological Station, C.S.I.C., c/ Americo Vespucio s/n, ES-41092 Seville, Spain. RL also at: LabOr – Laboratory of Ornithology, Dept of Biology, Inst. de Ciências Agrárias e Ambientais Mediterrânicas, Univ. de Évora – Núcleo da Mitra, Ap. 94, PT-7002-554, Portugal. E-mail: ruifazendalourenco@gmail.com

Abstract

The vocal behaviour of birds may be influenced by many factors, including the risk of being detected by a predator. In Doñana Protected Area, the tawny owl co-exists alongside its intraguild predator, the eagle owl Bubo bubo. We considered four scenarios to study the vocal behaviour of tawny owls at dusk by analysing: A) the calling rate of all males in 29 sites; B) the calling rate at dusk of males living within the home range of the intraguild predator; C) the calling rate of males living within the home range of the intraguild predator between 60 and 90 min after sunset; and D) the duration of male vocal bouts in visits where eagle owls have called. In scenario A we found that only the number of conspecific males affected the calling rate of tawny owls. In scenario B we observed that the presence of an eagle owl calling constrained the calling rate of the intraguild prey. In scenario C we found that this effect seemed mostly associated to a contemporaneous detection of the intraguild predator’s calls. Finally, in scenario D we found no significant effects on bout duration. These results seem to indicate that tawny owls use their intraguild predator’s calls as a cue to assess predation risk, and then adjust their vocal behaviour in order to minimize predation risk by a predator that may locate its prey by its vocalizations.

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