UW study finds songbird declines in high-density well sites

2011-10-11T17:45:00Z 2011-10-12T00:11:13Z UW study finds songbird declines in high-density well sitesBy MARTIN KIDSON Gazette Wyoming Bureau The Billings Gazette
October 11, 2011 5:45 pm  • 

CODY, Wyo. -- Drilling wells at high densities may contribute to a decline in bird species that depend upon sagebrush habitat, a new study from the University of Wyoming has found.

Directed by Anna Chalfoun of the Cooperative Fish and Wildlife Research Unit at the University of Wyoming, the study found that sagebrush habitat surrounded by high well densities -- especially natural gas wells -- supports lower densities of certain songbirds.

Completed over two years, the study encompassed the Pinedale Anticline and Jonah gas fields and the LaBarge oilfield in western Wyoming, where pad densities reach more than 16 wells per square mile.

Researchers found declines in population densities of Brewer's sparrows and sage sparrows, both of which are designated sensitive species by the Bureau of Land Management. They also found declines in vesper sparrow populations.

"We are currently investigating potential mechanisms underlying the observed density patterns, including increased nest predation rates and whether nest predators are more abundant in areas with natural gas activities," Chalfoun said.

According to the new study, oil and natural gas development in the intermountain West has expanded over the past two decades, primarily within landscapes dominated by sagebrush habitat.

Biologists have already documented the effects of energy development on high-profile game species, such as the greater sage grouse. But similar studies looking at nongame birds were lacking.

Many songbirds that breed within sagebrush habitat have shown range-wide population declines, the study found. It attributed the declines to widespread habitat loss and alteration.

Working in three energy fields in the Upper Green River Basin, researchers applied point-count sampling from May through July in 2008 and 2009.

Researchers recorded all birds seen or heard and noted the distance to the observer using digital rangefinders. Surveys began at sunrise on mornings without rain or strong winds and were completed within three hours.

The study found that well densities had negative effects on three of the most common species recorded, including the Brewer's sparrow, the sage sparrow and vespers sparrow. Horned larks increased with well densities, the study found, and sage thrashers showed no effects.

"We've been predicting for a long time that these heavy-handed well density projects are ecosystem destroyers," said Erik Molvar, a wildlife biologist with the Biodiversity Conservation Alliance. "This study shows that some of the smaller wildlife species lose their population density once you get a high density of well pads on the landscape."

Molvar believes the study demonstrates a need for the BLM to require directional drilling in future projects, reducing the footprint of oil and gas development on surrounding habitats.

New technology, he said, allows developers to consolidate drilling pads to a single location.

"The only roadblock for reforming the way drilling takes place on public lands today is a political one," Molvar said. "At what point are these federal agencies going to start managing these projects so it's compatible with wildlife?"

Cindy Wertz, public affairs specialist with the BLM in Cheyenne, said research from university partners plays a role in decisions made by the agency on public lands.

"We take all the information we get from studies and factor them into our land use plans," Wertz said. "We rely on our university partners and others to do this kind of thing for us and provide us the information. It's a valuable tool for us."

Contact Martin Kidston at mkidston@billingsgazette.com or 307-527-7250.

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