Contrasting impacts of invasive plants and human-altered landscape context on nest survival and brood parasitism of a grassland bird

Project Type: Graduate Student
Funds awarded in 2015: $9,977.00
Projected End Date: 12/31/2018
Grant Recipient: University of Illinois
Region: North Central
State: Illinois
Graduate Student:
Faculty Advisor:
Dr. James Miller
University of Illinois
Context Humans have altered grasslands in recent decades through crop conversion, woody encroachment, and plant invasions. Concurrently, grassland birds have experienced range-wide declines. Studies have reported effects of plant invasions and land conversion on nest ecology, but few have assessed relative impacts of these changes. Objectives We compared impacts of invasive plants and landscape context on nest survival of a grassland songbird, the dickcissel (Spiza americana). We also compared effects on parasitism by brown-headed cowbirds (Molothrus ater) and tested whether parasitism affects survival. Methods From 2013–2016, we monitored 477 dickcissel nests. We measured nest-site vegetation (including woody plants, tall fescue Schedonorus arundinaceous, and other invasive grasses) and measured landscape context at broad scales. Results Nest survival declined with increasing tall fescue cover at nest sites, and parasitism was more common at nests with greater fescue and woody cover. Some evidence suggested a negative effect of row-crop cover within 1000 m on nest survival, but no landscape patterns unambiguously affected survival. Woodland cover and wooded-edge prevalence were associated with reduced parasitism risk. Parasitized nests had smaller clutches, failed more frequently, and produced fewer fledglings than non-parasitized nests. Conclusions Determining the impacts of invasive plants and other anthropogenic changes on grassland birds will aid in prioritizing management to improve habitat quality. Our results indicate that optimizing landscape context around habitats may not affect dickcissel nest survival strongly, except perhaps through effects on parasitism. In contrast, controlling tall fescue and shrubs within grasslands could benefit birds by increasing nest success and reducing parasitism.
Peer-reviewed Journal Article
Scott B Maresh Nelson, University of Illinois at Urbana-Champaign
Jaime J Coon, University of Illinois at Urbana-Champaign
Courtney J Duchardt, University of Wyoming
James R Miller, University of Illinois at Urbana-Champaign
Diane M Debinski, Montana State University
Walter H Schacht, University of Nebraska-Lincoln
Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.