Nest Defense and Alarm Calling in Burrowing Owls: How Does Virulence of Nest Predators Alter Responses?

Natural selection has favored behavior in ground nesting birds to avoid detection by predators or defend their nests once detected. Burrowing owls (Athene cunicularia) nest in abandoned mammal burrows, and nest predation often determines their reproductive success. These owls defend their nests by altering posture, flight, aggression, and vocal displays. Their nest predators are ground dwelling (e.g., coyotes, Canis latrans and badgers Taxidea taxus) or aerial (great horned owls, Bubo virginianus, hawks, Buteo spp., falcons, Falco spp. and common ravens, Corvus corax). We consider coyotes, badgers, great horned owls and other raptors more virulent predators because they can kill adult owls as well as nestlings, whereas ravens kill only nestlings. We exposed burrowing owls to models of each predator type during field experiments conducted in the Morley Nelson Snake River Birds of Prey National Conservation Area to analyze characteristics of nest defense and alarm calls as a function of predator virulence, size, and attack mode to understand anti-predator behavior of owls