Date of Graduation

5-2021

Document Type

Thesis

Degree Name

Master of Science in Biology (MS)

Degree Level

Graduate

Department

Biological Sciences

Advisor

John D. Willson

Committee Member

Steven L. Stephenson

Second Committee Member

Brett A. DeGregoria

Keywords

Bayesian Hierarchical Model, Bird, Conservation biology, Fragmentation, Habitat Management, Multi-species Occupancy Model, Species Richness

Abstract

Agricultural expansion and increasing urbanization are driving rapid landscape modification in the Tallgrass prairies ecosystem and are affecting biodiversity at multiple spatial scales. Thus, the conservation of fragmented grassland and steeply declining grassland avifauna is dependent on the relationship between local- and landscape-scale factors and avian assemblage. We also need to understand how these factors, operating at different spatial scales, drive the occupancy of different guilds in the assemblage. We conducted repeated point count surveys during the breeding season of 2019 at 66 grassland sites across Arkansas and Missouri, USA. We developed a multi-species occupancy model to estimate species richness, and species- and guild-specific occupancy probability while accounting for species-specific detection probabilities. We examined the effect of landscape elements: type of landcover around a site, area and shape of a fragment and local-level elements: habitat type (remnant prairie/ hayfield), proximity to trees, and vegetation composition and structure on avian assemblage and guild-specific occupancy probability. Overall, we found that factors operating at landscape-scale have a significant effect on overall richness and composition of avian assemblage and guild-specific occupancy probability. The avian assemblage richness was higher for heterogenous landscape, small patches, and patches with more edge habitat which was a result of lower proportion of habitat specialists (grassland obligate) and higher proportion of habitat generalists. For grassland obligate species, high grassland cover, low forest cover, large patch area, less edge habitat, and lower litter depth had strong positive effects on their occupancy and guild-level species richness at a site. For grassland facultative species, high development around a site, small patch, high edge habitat, and lower litter depth had strong positive effects on their occupancy and guild-level species richness at a site. For woodland species, low grassland cover and high forest cover around a site, small patch, and high edge habitat had strong positive effects on their occupancy and guild-level species richness. Collectively, our results indicate that response to local- and landscape-scale factors varies between the guilds and habitat specialists are negatively affected by habitat fragmentation. Conservation efforts should focus on conserving landscapes, large tracts of prairies, minimize woody encroachment, reduce edge habitat and maintain heterogenous vegetation structure to mitigate grassland bird decline.

Available for download on Wednesday, May 17, 2023

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