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Jason Thiele

Document Type

Thesis - University Access Only

Award Date

2012

Degree Name

Master of Science (MS)

Department / School

Natural Resource Management

First Advisor

Kristel Bakker

Abstract

The burrowing owl (Athene cunicularia) is a species of conservation concern in South Dakota. The species’ range in the state is reduced from its historical extent, and it is now mostly restricted to the counties west of the Missouri River, where it usually nests in black-tailed prairie dog (Cynomys ludovicianus) colonies. Information about the burrowing owl’s current range and habitat needs in South Dakota is necessary to maintain the species as a relatively common component of the state’s avifauna. During the summers of 2010 and 2011, I surveyed for burrowing owls in 27 counties in western South Dakota that were known to contain prairie dog colonies. I found burrowing owls in 25 of the surveyed counties, but abundance varied across the study area. I used logistic regression models to examine how percent cover of grassland, cropland, trees, and prairie dog colonies at 4 spatial scales (buffers with radii of 400 m, 800 m, 1,200 m, and 1,600 m) impacted the probability of burrowing owls being detected in a prairie dog colony. Burrowing owls were most likely to occur in prairie dog colonies that had little tree cover within 800 m or 1,200 m, but model performance was relatively poor. Other, unknown landscape variables and/or habitat variables at a more local level are probably utilized by burrowing owls in the selection of a breeding site. To examine factors driving nest site selection at multiple spatial scales, I searched for owls in 107 prairie dog colonies from May through August 2011. I located nest burrows in owl-occupied colonies, and I randomly selected non-nest burrows in unoccupied colonies for comparison. I collected microhabitat data at each selected burrow, including vegetation composition, visual obstruction, burrow density, and distances to features thought to be potentially utilized or avoided by owls. I also calculated colony-level and landscape-level habitat metrics using a GIS, including colony size and percent cover of trees, grassland, and cropland within 400 m and 800 m of the selected burrow. I used logistic regression to identify variables that impacted nest site selection. Model fit and discrimination was satisfactory for competitive models. The models indicated that burrowing owls in South Dakota selected nest sites in landscapes with little tree cover, perhaps to avoid large avian predators. At the local scale, burrowing owls nested in regions of prairie dog colonies with relatively high percent cover of forbs and bare ground and relatively low visual obstruction readings. These characteristics are associated with prairie dog activity and may increase hunting success for burrowing owls. Current threats to burrowing owls in South Dakota include conversion of rangeland to cropland, loss of prairie dog colonies to sylvatic plague (Yersinia pestis) outbreaks and poisoning campaigns, and shooting by recreational prairie dog hunters. Maintaining active prairie dog colonies in open landscapes across western South Dakota is necessary to ensure preferred breeding habitat remains for burrowing owls.

Library of Congress Subject Headings

Burrowing owl -- South Dakota -- Geographical distribution
Burrowing owl -- Nests -- South Dakota
Burrowing owl -- Habitat -- South Dakota

Description

Includes bibliographical references (page 114-128)

Format

application/pdf

Number of Pages

140

Publisher

South Dakota State University

Rights

Copyright © 2012 Jason Thiele. All rights reserved.

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