Date of Award

Spring 5-8-2020

Level of Access

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Ecology and Environmental Sciences

Advisor

Katharine Ruskin

Second Committee Member

Maureen Correll

Third Committee Member

Brian Olsen

Additional Committee Members

Marissa Sather

Abstract

Grassland birds are declining precipitously in North America. Many grassland birds use the Northern Great Plains during their reproductive cycle, where much of their breeding habitat has been converted for agricultural use. Grassland landscapes that remain are sustained by management routines. Understanding habitat conditions that support multiple life stages throughout the entire reproductive cycle is essential for developing effective management strategies to lessen and reverse population declines in grassland bird populations. However, there is limited knowledge for habitat selection in grassland specialists, especially during the post-fledging stage. To address this information gap and to better inform managers with information than can support grassland birds during their breeding season, we measured habitat selection in both adults and juveniles of grassland bird specialized to the Northern Great Plains. We characterized nest site selection in four grassland specialists: Baird’s Sparrow (Centronyx bairdii), grasshopper Sparrow (Ammodramus savannarum), chestnut-collared longspur (Calcarius ornatus), and Sprague’s pipit (Anthus spragueii). We also examined habitat use of juveniles in Baird’s and grasshopper sparrows throughout the post-fledging phase using radio-tracking data. We analyzed habitat selection for adults and juveniles with parameters measured from the ground and from spectral data collected via Unmanned Aircraft System (UAS) at juvenile used points, random points, and adult nest sites. We found that adults of all four grassland specialists placed nests in intermediate ranges of vegetation height and density compared with habitat available on the landscape, demonstrating a community-level trend. Nest sites were also characterized by other habitat parameters though varied by species and spatial scales, indicating species-specific habitat selection as well. We found that juvenile birds used habitat that differed from both habitat available on the landscape and from adult nest sites. Particularly, high forb cover was influential for juveniles of both sparrow species and that with age, juveniles of both species moved toward lower elevations and that juvenile Baird’s sparrows moved towards densely vegetated areas (e.g. wetland areas). Additionally, we found that high-resolution Green Normalized Vegetation Index (GNDVI) was an informative habitat parameter for fine-scale habitat selection in grassland specialists and shows promise for UAS as an innovative tool for habitat assessment. Based on our findings, we recommend managers consider both community-level habitat selection to provide habitat that supports a suite of grassland birds and species-specific habitat selection to target particularly threatened species or those experiencing local declines. Further, we recommend consideration of all life stages for grassland birds that breed in the Northern Great Plains when strategizing a habitat management plan, particularly that wetland areas be regarded for the management of Baird’s sparrows.

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