Long-eared Owls, Asio otus: A Review of North American Banding

• Published in: The Canadian Field-Naturalist
• Main Author: Houston, C. Stuart
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Ottawa Field-Naturalists' Club 2005
• Subjects: Long-eared Owl; Asio otus; nomadism; irruption; Microtus; Short-eared Owl; Asio flammeus; Northern Harrier; Circus cyaneus; Saskatchewan
• Online Access: https://www.canadianfieldnaturalist.ca/index.php/cfn/article/view/151; https://doi.org/10.22621/cfn.v119i3.151

In Saskatchewan, at the northern edge of the species’ range, the Long-eared Owl (Asio otus) is an irruptive species that has appeared in numbers during major vole (Microtus) outbreaks in 4 of 44 years. Seven other years have had either no bandings or no sightings over large areas. In a search for possible evidence of food-based nomadism, population trends, length and synchronicity of cycles, and longevity, I reviewed all banding in North America through 1998. Prior to banding office computerization (retroactive to 1955), 803 Long-eared Owls had been banded with 33 band encounters (4.1%). Between 1955 and 1998 there were another 10,250 banded by 426 banders with 86 band encounters (0.8%). Encounter records, especially those involving unexpected directions and distances, tend to support but do not prove food-based nomadism. Peaks of migration movements at different long-term stations occurred in different years. There is soft evidence of both 10- and 3-yr cycles. There is inconclusive evidence for a continuing population decline. The oldest banded bird in North America lived for 11 years, 1 month, but another possibly lived for 15 years, 8 months.