Influences of Energy Development on Songbird Communities in Sagebrush Ecosystems
Photo of sage thrasher perched on sagebrush.

Three migratory songbird species, sage thrasher (above), sagebrush sparrow, and Brewer’s sparrow are considered near-obligates of sagebrush shrubland. Healthy populations of these species can indicate healthy sagebrush ecosystems.

Project Partners

University of Wyoming

Wyoming Game and Fish Department

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Contact Anna Chalfoun

307-766-6966

 

Why are Sagebrush Songbird Communities a Concern in Wyoming?

Healthy Songbird Populations Indicate Healthy Sagebrush Ecosystems—The Brewer’s sparrow, sagebrush sparrow, and sage thrasher are songbird species that nest almost exclusively in sagebrush habitats. Stable or increasing populations of these species, therefore, indicate that their sagebrush habitats are intact and healthy. Because Wyoming encompasses some of the largest remaining areas of intact, functioning sagebrush habitat, it plays a crucial role in conserving sagebrush songbird communities.Since European settlement, however, at least 50% of North America’s sagebrush habitat has been fragmented by development and conversion to croplands. As a result, sagebrush songbird populations have been declining throughout their ranges and all three species are designated as Species of Greatest Conservation Need by the Wyoming Game and Fish Department. In the WLCI region, the quality of sagebrush habitats is a concern given the widespread extent of habitat conversion and alteration in sagebrush systems, in part the result of energy resource development. Energy development is suspected of contributing to songbird declines, but exactly how it may be influencing their populations is unknown.

Energy Development May Alter Nest Predator Communities in Sagebrush —USGS researchers and students from the University of Wyoming have spent the last decade establishing and monitoring songbird study sites in oil and gas production fields of the WLCI region. When landscapes are fragmented by land-uses that drastically alter the original landscape configuration and/or convert habitats from one type to another, the checks and balances that regulate populations may be upset. For sagebrush songbirds,  hypothesized cause of population declines included reductions in food resources changes to the nest predator community

Key Findings

  • Numbers of Brewer’s and sagebrush sparrows decreased with increasing well density and proximity to the nearest well pad.
  • For all three sagebrush songbird species, >90% of nesting failures resulted from nest predation.
  • Nest predation increased with increasing well density and proximity to the nearest well pad.
  • Overall, nest survival rates for all three species decreased with increased surrounding habitat loss due to natural gas development; though the strength of the pattern varied across years for Brewer’s sparrows.
  • Sage thrasher nestling mass decreased with well density, suggesting potential food limitation where energy development is more intense.
  • The predominant nest predators were rodents (deer mice, chipmunks and ground squirrels).
  • Counts of nest predators revealed increased numbers of deer mice and ground squirrels at sites with more habitat loss due to development.

Study Objectives

The ultimate goal of this work is to understand the complex interactions between habitat change, songbird nesting success, and nest predators. In turn, this information will help resource managers and land-use planners provide more effective conservation strategies for maintaining the integrity of sagebrush habitats for nesting birds.

  • Evaluate the influence of energy development on sagebrush songbirds within oil and gas fields in the WLCI region.
  • Establish study sites that represent a low-to-high gradient of energy-development intensity (surrounding habitat loss).
  • Evaluate habitat characteristics across the energy-development gradient.
  • Measure songbird diversity, abundance, and nesting success across the energy-development gradient.
  • Document nest predator species and their abundances across the energy-development gradient.
  • Analyze differences in and relationships among habitats, predators, and songbird population dynamics across the energy-development gradient.
  • Determine whether high rodent populations in oil and gas fields is caused by lower abundance of primary predators or by food augmentation.
Map of songbird sampling sites in energy development areas within the WLCI.

Energy-development areas where songbird sampling occurred: LaBarge Field (left), Pinedale Anticline (upper right), and Jonah Field (lower right). Well-pad densities per square kilometer range from 1 to more than 15 (light to dark blue). Click to enlarge.

Study Findings and How They Apply to Sagebrush Songbird Conservation

Sagebrush songbird abundance and nesting success declined along a gradient of increasing energy development intensity. This was due, at least in part, to increased rodent abundance and predation on nests as the density of well pads and other infrastructure increased. Current efforts are focused on what might be augmenting rodent populations in natural gas fields. Understanding the mechanisms that underlie the effects of energy development on native birds will allow scientists to better inform managers and lead to more specific mitigation recommendations for maintaining healthy populations of sagebrush songbirds where energy extraction is taking place. We will provide the results of this work to Wyoming Game and Fish Department for use in updating the Wyoming State Wildlife Plan.

Photo from video camera of deer mouse taking nestling from nest.
Photo of researcher looking for nests in sagebrush.
Photo of sagebrush sparrow nest with eggs.

A deer mouse caught on video taking a nestling from its nest. Our study employs video cameras to monitor nest predation.

Researchers monitor nests of sagebrush songbird species to determine nest success.

Sagebrush songbird abundance and nesting success declined along a gradient of increasing energy development intensity. Our results indicate increased nest predation among the immediate causes of this decline.