Migration and Roosting Behavior of Northern Saw-Whet Owls (Aegolius acadicus) during Fall Migration in Western Montana

Abstract

We studied Northern Saw-whet Owl (Aegolius acadicus) movement and roosting behavior over two fall migrations in the Bitterroot Valley of western Montana, USA. We tracked 65 migrating owls using aerial and ground telemetry, including 55 owls for multiple nights. Owls tracked on sequential nights moved an average of 13.2 km/night ± 13.0 (SD) and the maximum distance moved in one night was 65.7 km. Owls tracked multiple nights traveled due south less often than southeast or southwest and used foothill topography on both the east and west sides of the valley. Thirty-five (64%) of the owls tracked for multiple nights showed stopover behavior involving 40 individual stopover events (five owls made two stopovers). We examined roost-site characteristics in floodplain forest. Roosts most often occurred high in ponderosa pines (Pinus ponderosa) with little to no obvious whitewash or pellets present, suggesting that passive search methods would overlook many of the roost locations.