Presentation Abstract

Title: Increased nest predation and natural gas development; what’s in the pipeline for sagebrush obligate songbirds?
Session Title: "Ecology, Conservation and Management of Birds"
Session Number: 44
Session Time: Monday, Oct 15, 2012, 1:00 PM - 5:00 PM
Presentation Time: Monday, Oct 15, 2012, 1:00 PM - 5:00 PM
Presentation Number: 31
Author(s): Matthew G. Hethcoat, Anna D. Chalfoun, University of Wyoming, Laramie, WY, Contact: mhethcoa@uwyo.edu
Abstract Body: Natural gas development has rapidly increased within sagebrush dominated landscapes of the Intermountain West. Prior research in the Upper Green River Basin, WY, demonstrated increased nest predation of sagebrush-obligate songbirds with higher densities of natural gas wells. To better understand the mechanisms underlying this pattern we tested alternative hypotheses regarding changes in predator abundance and habitat structure across a gradient of natural gas development intensity, indexed by well density. We monitored nests of Brewer’s sparrows (Spizella breweri), sage sparrows (Amphispiza belli), and sage thrashers (Oreoscoptes montanus) at twelve sites within two energy fields. We conducted a variety of predator surveys and measured microhabitat metrics at nest sites and paired random points. Using logistic exposure we modeled the effects of well density, predator abundance, and microhabitat features in relation to a constant survival model. Daily nest survival decreased with increasing well density for sage sparrows and sage thrashers. Top supported nest survival models varied among focal species with strong support for shrub density, seasonal variation, and shrub cover for Brewer’s sparrow, sage sparrow, and sage thrasher respectively. Both shrub density and shrub cover decreased with increasing well density, suggesting the potential for bottom up forces to be affecting nest predation rates of songbirds breeding in energy fields. Despite increased detections of common ravens (Corvus corax) and sciurid mammals (Tamias spp. and Spermophilus spp.) with increasing well density, there was relatively little support for models which included predator abundance metrics. Shrubland bird populations are among the most rapidly declining groups of avian species in North America. With increasing demands for domestic sources of energy, the identification of specific mechanisms influencing nest predation is a critical next step in developing clear strategies for mitigating the impacts to songbirds breeding in energy fields.



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