| Over the past half a century, the Short-eared Owl (Asio flammeus ) has experienced a severe population decline across North America. Many aspects of Short-eared Owl natural history are poorly understood, thus hampering the development of effective management plans. The overall goal of this thesis was to help to fill the knowledge gaps that exist, and at the same time provide a foundation for future studies. The specific objectives were three-fold: (1) to investigate Short-eared Owl spatial origins across North America in the context of nomadic, migratory and/or philopatric movements; (2) to develop a practical visual survey protocol aimed at improving monitoring efforts and facilitating assessments of across season landscape-level habitat use; and (3) to describe nest site characteristics, success, and causes of failure. Stable isotope analysis was used to investigate spatial origins of Short-eared Owls, and while exploratory in nature, evidence was provided that the species may exhibit different movement strategies across their North American range. The volunteer visual survey protocol developed here was successful over a trial period, and should become a reliable monitoring scheme to track abundance and distribution through time. Based on the comparison of sites 'used' versus 'available' on two islands on Lake Ontario near Kingston, in eastern Ontario, the Short-eared Owl's use of forest cover during the winter appears to be dependent on seasonal effects. Also, during the breeding season in this geographical area, grazed grassland with scattered trees should be considered important habitat. Short-eared Owls exhibited a tendency for loose nesting aggregations in areas that were predominantly tall grasses, and often on grazed grassland. Fledging success was low and both anthropogenic and natural causes of mortality were identified. The findings of this study will contribute greatly to the current understanding of Short-eared Owl natural history, and the techniques described will be valuable tools for subsequent research and conservation initiatives. |
