Document Type

Thesis

Date of Award

Summer 8-2019

Degree Name

Master of Science (MS)

Department

Biology

First Advisor

Alison Scoville, PhD

Second Advisor

Jason Irwin, PhD

Third Advisor

Michael Gregg, PhD

Abstract

The ecology and space use of Common ravens (Corvus corax; hereafter ravens) is not well understood in the shrub-steppe of central Washington State. Raven populations have increased by more than 254% since 1990 in Washington State (North American Breeding Bird Survey; www.mbr-pwrc.usgs.gov/bbs/). Ravens in central Washington are implicated as top predators of a small endemic population of greater sage-grouse (Centrocercus urophasianus). Researchers have related increased raven populations to anthropogenic subsidies such as landfills, agriculture, and livestock operations. Analyzing movement can help researchers understand the characteristics of habitat that are important and potentially drive population fluctuations. We found that daily and monthly movement distances for ravens were 19 kilometers (range = 3–238.5 km) and 505 kilometers (range = 102–1,575.4 km), respectively. Calculating Brownian Bridge home ranges shows that the average non-breeding raven home range size was 1,746 km2 (range= 104–6,675 km2), which is like home ranges from other studies. Annual reproductive output of ravens on YTC has been documented through nest monitoring since 2011. To better understand the factors that may be influencing raven reproduction, nest success was modeled against parameters thought to be important for ravens. YTC has a relatively high density of nesting ravens compared to other regions, and averages iv 51.5% annual nest success. We found that no habitat variables used for this analysis influenced raven nest success.

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