Anti-predator responses of neotropical resident and migrant birds to familiar and unfamiliar owl vocalizations on the Yucatan Peninsula

To reduce predation risk, animals must employ effective predator-detection strategies. Many species rely on prior experience, or learning, to detect predation risk, but this strategy is ineffective when exposed to an unfamiliar potential predator. Many species, however, exhibit an innate response to potential predator species but to our knowledge, no studies have examined the response of birds to unfamiliar, allopatric predator species. In this study, we exposed migrant and resident tropical birds on the Yucatan Peninsula, Mexico, to vocalizations of two owl species: the resident Ferruginous Pygmy-owl (Glaucidium brasilianum), assumed to be familiar to both migrants and residents, and the allopatric Eastern Screech-owl (Megascops asio), likely to be familiar only to migratory birds that breed in eastern temperate North America. Most birds responded only to predator vocalizations with which they were expected to be familiar: both migrants and residents responded strongly to Ferruginous Pygmy-owl vocalizations; the Eastern Screech owl vocalization elicited a response only from migrants. These results suggest that tropical residents are unable to recognize innately, or to infer danger from, vocalizations of novel predators. As species ranges expand and exotic predators are introduced to new areas, it will be important to better understand the predator recognition response of potential prey species.