科研之友
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摘要
Despite the widespread distribution of Northern Saw-whet Owls (Aegolius acathcus), little is known about their population numbers, trends, or migratory behavior within the Canadian prairies. We studied saw-whet owl population trends and migratory behavior in the north-central portion of the species range, and evaluated possible mechanisms explaining these observed patterns. We examined population trends, demographics, and migratory timing using 9 yr of banding data collected by the Delta Marsh Bird Observatory (DMBO) migration-monitoring program. We documented a regularly timed autumn migration consisting of primarily hatch-year males and females and adult females. Large annual fluctuations in owl abundance resulted in low statistical power to detect trends. We detected no significant trend in total owl numbers; however, we detected significant increases in the numbers of second-year and after-second-year females. We compared DMBO migration data to spring abundance data from the Manitoba and Saskatchewan Nocturnal Owl Survey (NOS). Significant positive correlations between the DMBO and NOS datasets provided confidence that our annual owl abundance estimates were representative of actual changes in owl abundance, and suggested that population trends were synchronized over large geographic regions spanning both provinces.
- 出版日期2012-3
