Date of Award

Spring 5-3-2024

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Wildlife Ecology and Wildlife Conservation

Advisor

Amber Roth

Second Committee Member

Erik Blomberg

Third Committee Member

Joseph Zydlewski

Abstract

The Golden-winged Warbler (Vermivora chrysoptera) is a Nearctic-Neotropical migratory songbird that has experienced over 70% population loss since the 1960s. While primary drivers of decline are unclear, habitat loss and hybridization with the genetically similar Blue-winged Warbler (Vermivora cyanoptera) are likely causes. This species breeds in two geographically allopatric regions, the Great Lakes and the Appalachian Mountains. These two populations are experiencing different rates of decline, with the Appalachian Mountain population facing steeper decline than the Great Lakes. Due to pronounced range-wide population decline, Golden-winged Warbler is currently under review for protection under the Endangered Species Act, however information pertaining to adult annual survival and variations that may occur temporally, geographically, or demographically is currently lacking. Specifically, survival information for female Golden-winged Warblers is uncommon given that females are elusive in nature and thus are largely absent in historical capture-mark-recapture datasets. To better understand sex-, site-, and region-specific variations in apparent annual survival, we conducted a range-wide, hierarchical multi-population Cormack-Jolly-Seber analysis that encompassed 23 sites across Golden-winged Warbler breeding and wintering grounds. Each site represented a capture-mark-recapture dataset collected between 1980-2022 by a large network of researchers studying various aspects of Golden-winged Warbler demographics. We found a tendency for apparent annual survival to be higher in the Appalachians region but overlapping credible intervals did not support a substantial difference. More standardized data collection across datasets and an increase in the number of years represented in individual capture histories would have increased our certainty in the presence or absence of regional variation. Male apparent annual survival tended to be higher than females but was not substantially different. However, this was a male-biased analysis with only 20% female representation across the compiled dataset. To increase female representation in survival analyses, we used VHF-telemetry to increase annual female detectability and ran additional apparent annual survival and return rate analyses to better understand differences in sex-specific variations. This analysis encompassed data collected across 13 sites in their breeding range from 2021-2023. With different methods used to detect females, along with a concentrated effort to mark females, we were able to achieve 45% female representation in our apparent annual survival analysis and 37% female representation in our annual return rate analysis. Results showed that females had substantially lower apparent annual survival and return rate probabilities than males, which suggests that females are experiencing either increased mortality at some point during their full annual cycle, or they have a higher dispersal rate than males. These findings provide crucial insights into how sex influences the survival and return rate of Golden-winged Warblers and underscore the need for more female-focused survival studies.

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