Sex and Nest Stage Differences in the Circadian Foraging Behaviors of Nesting Burrowing Owls

Abstract

AbstractAbstractWe used infrared cameras to accurately record the circadian provisioning behaviors of nesting Burrowing Owls (Athene cunicularia) in southern Saskatchewan, Canada. We monitored 19 nests over three years and recorded 4675 prey deliveries. We found a sex-based difference in foraging behavior: males hunted vertebrates during crepuscular periods, and females hunted insects during diurnal periods. Males delivered between 82% and 96% of all vertebrate prey depending on the stage of the nest. Males delivered at least 90% of all insects during early nest stages, after which females delivered an average of 76% of the insects. The rate of vertebrate deliveries increased from 1.3 to 7.7 per 24 hr as the summer progressed, and the number of insect deliveries increased from less than 1 to 18.6 per 24 hr. Vertebrates comprised 98%–99% of prey biomass delivered until females began delivering insects, but even then vertebrates still comprised 94% of prey biomass. Insects were consistently delivered at the highest rate during the day and vertebrates were consistently delivered at the highest rates during the dusk and dawn periods.