Date of Award

5-2018

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biological Sciences

Committee Member

David Jachowski, Committee Chair

Committee Member

Patrick Jodice

Committee Member

Beth Ross

Committee Member

Cathy Bodinof Jachowski

Abstract

The loggerhead shrike (Lanius ludovicianus) is a species of concern throughout its range due to severe population declines over the past seven decades. Grassland habitat loss and fragmentation is widely viewed as contributing to the decline. Habitat associations have primarily been studied up to the territory scale, with few studies assessing shrike habitat selection at landscape scales. In Chapter 1 we conducted roadside passive-active point counts for loggerhead shrikes in the coastal plain of South Carolina to evaluate support for several competing hypotheses of how land use and habitat fragmentation at multiple spatial scales influenced the occupancy of loggerhead shrikes. Detection probability increased with fair weather and temperature, and decreased with noise. High probability of detection (p=0.49, SE=0.08) indicated support for the application of passive point counts in future loggerhead shrike monitoring. Occupancy was best predicted by percentage of pasture at 1 km, where predicted occupancy increased from 2%, when there was 0% pasture in a 1 km radius, to 98%, occupancy when there was 43% pasture in a 1 km radius. There was considerable model selection uncertainty, and our model averaged occupancy estimate was low (ψ=0.17, SE=0.05). Extrapolation of our averaged model suggested that only 8% of the South Carolina coastal plain was occupied by loggerhead shrikes in the 2016 and 2017 breeding seasons. Our results highlight the importance of habitat beyond breeding territories, and highlight the need for higher concentrations of pasture and grassland at a 1 km scale in order to increase the proportion of area in South Carolina occupied by shrikes.

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