Investigating impacts of environmental biotic and abiotic factors on the breeding habitat and diet of declining grassland birds
Angell, Joshua Newlin
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Permalink
https://hdl.handle.net/2142/130062
Description
Title
Investigating impacts of environmental biotic and abiotic factors on the breeding habitat and diet of declining grassland birds
Author(s)
Angell, Joshua Newlin
Issue Date
2025-07-23
Director of Research (if dissertation) or Advisor (if thesis)
Sperry, Jinelle
Committee Member(s)
Ward, Michael
Katz, Aron
Department of Study
Natural Res & Env Sci
Discipline
Natural Res & Env Sciences
Degree Granting Institution
University of Illinois Urbana-Champaign
Degree Name
M.S.
Degree Level
Thesis
Keyword(s)
Birds
grasslands
community ecology
nesting ecology
diet
DNA metabarcoding
arthropods
Abstract
Grassland birds are declining faster than any other group of birds in North America, primarily due to massive habitat loss as native prairies have been converted to agricultural land and other human developments. To maximize the effectiveness of what little suitable grasslands remain, conservation efforts will rely on a thorough understanding of how various environmental characteristics influence the quality of breeding habitat for these declining species and the implementation of emerging tools to assess reproductive dynamics. To holistically examine the ability of grassland habitats to support nesting birds, I monitored the nests of four species (grasshopper sparrow, field sparrow, vesper sparrow, and eastern meadowlark), conducted vegetation surveys, and sampled the local arthropod communities at Fort McCoy, Wisconsin, in 2023 and 2024. I also collected fecal samples from nestlings to determine provisioned diet using fecal DNA metabarcoding. Grasshopper sparrows were found to place their nests in areas with greater warm-season grass cover and deeper litter. Increased litter at the nest and denser surrounding vegetation were associated with lower daily predation risk for this species. All four species preferred to feed prey from Lepidoptera and Araneae to their nestlings, while three species provisioned Orthoptera at a higher rate. Other arthropod orders tended to be avoided relative to their abundances, with Hymenoptera and Coleoptera showing the strongest negative preferences. The composition of grasshopper sparrow nestling diets was best explained by yearly variation, which coincides with notable climatic differences between 2023 and 2024. These results exhibit the importance of both biotic and abiotic factors on grassland bird breeding and productivity and inform considerations related to habitat management and continued climate change.
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