Document Type

Thesis

Date of Degree Completion

Spring 2021

Degree Name

Bachelor of Science

Department

Biology

Committee Chair

Alison Scoville

Second Committee Member

Taza Schaming

Abstract

The Clark’s nutcracker (Nucifraga columbiana) and whitebark pine (Pinus albicaulis), both native to the harsh subalpine habitats of Washington’s Cascade Mountains, are being negatively impacted by white pine blister rust (Cronartium ribicola), the mountain pine beetle (Dendroctonus ponderosae), and climate change. As temperatures continue to warm, while many species at lower elevations can move upward in elevation to suit their temperature needs, subalpine species do not have that option. Whitebark pine is a keystone tree species - numerous animals consume its high fat, high energy seeds; it’s a nurse tree, providing shelter and protection to smaller trees and plants; and it helps maintain the snowpack at higher elevations. The Clark’s nutcracker is the only significant seed disperser of whitebark pine - it will not reproduce without the bird’s dispersal and caching behavior. In an effort to protect whitebark pine, several restoration projects are being carried out across their range, including seed collection, planting, and prescribed burns. It is critical for whitebark pine management to take nutcracker behavior and their interaction with abiotic and biotic factors into account during restoration planning. The goal of our project is to determine how variation in whitebark pine habitat in the North Cascades impacts Clark’s nutcracker occupancy. This study, and a concurrent study in Glacier National Park, are the first to use automatic acoustic monitoring devices, versus in-person surveys, to survey nutcrackers. We used acoustic monitors to continuously survey for nutcracker calls to document their occurrence. We deployed the monitors at twelve sites in the Cascade Mountains southwest of Ellensburg, WA between June 19th and October 24th, 2020 to gather audio data (n = 781 days). Additionally, we conducted belt transects and whitebark pine cone counts to quantify habitat characteristics, as well as in-person occupancy surveys to compare with the monitor data. We included date, weather, local level whitebark pine density and cone presence/absence, and landscape-level ponderosa pine and Douglas-fir density in our models. We used an occupancy model to evaluate influences on detection (p), colonization (γ; probability of being present in a previously unoccupied site), and extinction (ε; probability of being absent in a previously occupied site). We found that weather was the only strong predictor of detection, there were no strong predictors of colonization, and date was the only strong predictor of extinction. As the summer season ends, nutcrackers use lower elevation habitat more often, visiting higher elevation sites less frequently (Lorenz and Sullivan, 2009), which may explain why date was a predictor of extinction.

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