Publication Date

8-2013

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Raptor Biology

Department

Biology

Major Advisor

Julie A Heath

Abstract

Studies across multiple spatial and temporal scales will improve understanding of the drivers of global change including habitat degradation, invasive species, and climate change. How global drivers affect the ecology of wintering raptors in western North America and the Great Basin may have important implications for changes in distribution and abundance, and consequently population persistence. I examined the winter distributions of six western North America raptor species using Christmas Bird Count data from 1975-2011 to assess range shifts over time and in relation to temperature. Also, I considered whether population patterns within Bird Conservation Regions (BCR) were best explained by changes in distribution or changes over time. I used an historical dataset from 1991-1994 and current information from 2010-2012 to examine whether wintering raptor occupancy patterns were consistent with regional changes in distribution and climate or habitat conditions within a local management unit, the Morley Nelson Snake River Birds of Prey National Conservation Area (NCA). All six wintering raptor distributions in western North American have shifted north over time and five of six raptor species tended to winter further north during warmer winters. Northward shifts were predictive for 39% of regional population indices, and locally I observed increased occupancy for most wintering raptors in the NCA despite continued habitat degradation. Three raptor species also changed their habitat use over time by using more or less agriculture or more areas dominated by invasive plants. Changes in habitat use may at least partially mediate their apparent response to climate change. Raptors may be particularly responsive to warming winters because of life history flexibility, high competition for nesting sites that drives males to winter farther north, or both. Organisms with broad geographic ranges that are flexible in their habitat use stemming from changing landscapes appear better able to respond to global forces such as climate change. Our ability to manage bird populations within local bird conservation regions and management areas will fundamentally change as more species exhibit ecological changes in response to global change.

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