Date of Graduation

12-2018

Document Type

Thesis

Degree Name

Master of Science in Biology (MS)

Degree Level

Graduate

Department

Biological Sciences

Advisor/Mentor

John D. Willson

Committee Member

Steven J. Beaupre

Second Committee Member

Sarah E. Durant

Keywords

Ecology, Migration, Movement Ecology, Owl, Ozark Highlands, Saw-whet Owl

Abstract

Studying movement ecology is important not only in understanding the distribution of a species, but in understanding the magnitude of migration through certain regions, as well as explaining regional differences in demographics. The Northern Saw-whet Owl (Aegolius acadicus) is a small, migratory forest owl found throughout much of North America. Despite being captured widely during fall migration, the species’ movement ecology is poorly understood. Exploratory studies outside the saw-whet owl’s normal range have successfully captured the species during fall migration. In the Ozark Highlands ecoregion of the central United States, their status has been considered vagrant during fall and winter. Since 2010, saw-whet owls have been captured successfully in the region, historically considered south of their normal range. We sought to assess fall migration and demographics of 412 saw-whet owls captured at four study sites in the Ozark Highlands of Missouri, northern Arkansas, and eastern Oklahoma. Saw-whet owls were captured from mid-October to early-December in the study region. Capture rate varied by latitude and among sites. Demography of owls travelling through the region varied by migration type, with an increase in captures and proportion of hatch-year individuals during irruption years. In addition to likely being a regular fall migrant through the Ozarks, we documented saw-whet owls wintering in the southwestern Ozarks. During autumn migration of 2016 and 2017, we deployed 27 radio transmitters on saw-whet owls captured at our Arkansas banding site. Detections were obtained from 17 tagged individuals during the following winters. Saw-whet owls remained in the region from 1 to 112 days after release, suggesting the species winters to some extent in northwestern Arkansas. Based on assessment of landscape and habitat variables at diurnal roost sites, the species seems to prefer open shortleaf pine (Pinus echinata) habitat. Further study is required to determine the full extent of the saw-whet owl’s winter range; however, ample pine forest and cedar glades could provide optimal wintering habitat throughout the Ozark Highlands.

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