Publication Date

Fall 2016

School

School of Health Sciences

Major

Biology: Environmental Science

Keywords

Northern Saw-whet Owl, migration, autumn migration dynamics, environmental factors, owl banding, moon illumination impact on migration, wind direction impact on migration

Disciplines

Animal Sciences | Life Sciences | Ornithology

Abstract

A portion of the population of the Northern Saw-whet Owl (Aegolius acadicus) leaves its breeding range in Canada and the northern United States each fall to winter where lesser snow cover allows easier access to prey. Study of its migratory dynamics is difficult, however, both because of its nocturnal habits and because it does not vocalize readily off of its breeding territory. Since 2002 banding studies in the Lynchburg area have investigated the migration dynamics of this species in central Virginia. However, few studies have examined the influence of environmental factors on capture rates of saw-whets during migration. Data were analyzed for the falls of 2007 and 2012, which were the two years of greatest migration volume in central Virginia, being “irruption years” in this species’ migratory cycle. In both years, nightly owl capture rates were strongly correlated with prevailing wind direction, with highest capture rates occurring during nights in which winds were predominantly out of the northeast quadrant. In 2012, nightly owl capture rates were also strongly negatively correlated with moon illumination, with highest capture rates occurring during nights of least moon illumination. For both years’ data combined, owl capture rates were also weakly negatively correlated with wind speed, Julian date, and temperature. Possible reasons for these relationships are considered.

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