Document Type

Thesis - Open Access

Award Date

2025

Degree Name

Master of Science (MS)

Department / School

Natural Resource Management

First Advisor

Amanda Cheeseman

Abstract

The pinyon jay (Gymnorhinus cyanocephalus) is a highly social, colonially nesting corvid endemic to the interior western United States whose populations have declined by ~72% since 1966, prompting the species’ current review for listing under the Endangered Species Act. Pinyon jays inhabit pinyon pine (Pinus subsect. Cembroides) and juniper (Juniperus spp.) woodlands and other dry conifer woodlands, portions of which are treated through tree thinning and removal for fuels reduction, ecological restoration, and habitat improvement for wildlife. As a result there is pressing need to better understand how woodland treatment and other potential drivers impact pinyon jay habitat suitability and use, particularly during the sensitive breeding season. The goal of this thesis is to evaluate predictive drivers of habitat suitability for breeding pinyon jays at multiple scales and assess the effects of woodland treatment and other key variables on breeding-season habitat use. In chapter two, I evaluated environmental, topographic, climatic, and anthropogenic variables and developed predictive maps of habitat suitability for colonies across Colorado using random forest models at two spatial scales. A heterogeneous mosaic of tree-cover classes in drier areas with gentle slopes, lower shrub cover, and moderate tree cover predicted higher suitability, indicating that mixed-structure woodlands with an even distribution of varied tree-cover classes support key breeding resources. The predictive habitat suitability maps generated in this study provide land managers with valuable tools for aligning numerous management objectives with the ecological requirements of pinyon jays at multiple spatial scales. These maps can assist in implementing timing restrictions for woodland treatments and other anthropogenic disturbances in areas of high suitability, guide management decisions toward locations where preserving or enhancing canopy heterogeneity will support breeding-season resource needs, and identify priority areas for continued research or pre-treatment surveys to advance critical conservation efforts for pinyon jays. For chapter three, I evaluated the influence of woodland treatment and other environmental, topographic, climatic, and anthropogenic variables on habitat use during the breeding season in south-central Colorado using single species, single season spatial occupancy models. Results showed that pinyon jays were more likely to use areas near human development, suggesting that modified landscapes may provide supplemental food and water resources. Higher predicted use near treatment areas, combined with the positive association with tree-cover diversity, suggests that strategic woodland treatments designed to maintain a balanced mosaic of low (0–15%), moderate (15–30%) and high (> 30%) tree-cover patches may support the varied resource needs of pinyon jays during the breeding season. While further research evaluating the influence of woodland treatments on pinyon jay demographics and reproductive success is warranted, this study offers practical tools and ecological insight for guiding pinyon-juniper woodland management in Colorado and implementing strategic woodland treatments that maintain suitable breeding habitat for pinyon jays, contributing to broader conservation efforts for this declining species.

Library of Congress Subject Headings

Pinyon jay -- Breeding -- Colorado. 
Pinyon jay -- Effect of forest management on -- Colorado. Pinyon jay -- Habitat -- Colorado. 
Forest thinning -- Colorado. 
Wildlife habitat improvement. 
Habitat suitability index models.      

Publisher

South Dakota State University

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Rights Statement

In Copyright