Year of Award

2023

Document Type

Dissertation

Degree Type

Doctor of Philosophy (PhD)

Degree Name

Wildlife Biology

Department or School/College

Wildlife Biology Program

Committee Chair

Victoria Dreitz

Commitee Members

Lorelle Berkeley, Michael Mitchell, Krishna Pacifici, Steven Running

Keywords

conservation, model, remote sensing, reproduction, sagebrush, songbird

Abstract

Anthropogenic land cover change continues to degrade and fragment wildlife habitats, threatening biodiversity at local, regional, and global scales. Songbird populations are sensitive to broad habitat changes and therefore can be used to assess and prioritize habitat for biodiversity. For example, biodiversity losses in the arid grass and sagebrush of western North America (Artemisia spp.; hereafter “sagebrush steppe”) are reflected in the rapid decline of songbird populations. However, the influence of the principal land use, livestock grazing, on songbird populations, and by inference biodiversity, is unclear. In this dissertation, I investigated sagebrush steppe songbird conservation in a grazed landscape by applying statistical models to a combination of field and remote sensing data. Chapter 1 provides an initial investigation of how different livestock grazing metrics influence the productivity of the sagebrush steppe, which provides some indication on how grazing broadly affects wildlife habitat. I found abiotic factors such as temperature and moisture had a much larger effect on sagebrush steppe productivity than grazing and that there were often significant interactions between grazing and abiotic factors. Then, I directly assessed which abiotic or biotic factors were most important to sagebrush steppe habitat quality through the estimation of sagebrush steppe songbird reproductive metrics. To do this, I developed and tested a novel reproduction model in Chapter 2 that allowed the integrated estimation of nest success, detection, and abundance using data commonly collected for time-to-event nest success models. In Chapter 3, I applied that model to seven years of sagebrush steppe songbird nesting data collected near Roundup, Montana. Similar to findings in Chapter 1, abiotic factors had the most influence on songbird reproduction, namely interannual vegetation productivity. Overall, this work suggests that grazing management in our area of the sagebrush steppe is being conducted at sustainable levels and that future conservation actions should focus on protecting areas that support high biodiversity from more detrimental land use or land cover change.

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