By Laura Zuckerman
SALMON, Idaho (Reuters) - Key populations of songbirds are in decline in the sagebrush plains of southwestern Wyoming as oil and gas development there increases, a University of Wyoming scientist said on Thursday.
A study led by Anna Chalfoun, an avian ecologist with the Wyoming Cooperative Fish and Wildlife Research Unit, is thought to be the first to shed light on how the energy boom in the Intermountain West is affecting songbirds that rely on sagebrush for feeding, mating and nesting.
The research, published in a recent edition of The Journal of Wildlife Management, may aid in shaping the design of future oil and gas fields in Western states.
Sagebrush ecosystems there have been fragmented or otherwise altered to allow for development of everything from cities to wind farms.
Energy activities have ramped up for two decades on sage-covered public lands in southwestern Wyoming, where biologists have already tracked damage to the habitat of game birds such as the greater sage grouse.
Now Chalfoun and University of Wyoming colleagues are sharpening the focus on migratory songbirds like Brewer's sparrows and sage sparrows, both classed as sensitive species by the Bureau of Land Management. The birds are suffering range-wide declines of up to 3 percent a year, the study said.
The scientists linked dwindling numbers of those sparrows and vesper sparrows in two gas fields and an oil field in Wyoming to the density of drilling wells, which the study used to gauge the level of petroleum exploration and production in a given area.
Researchers found the steepest declines where the presence of wells, roads and human activity was greatest.
The Jonah field south of Pinedale, Wyoming, ranks among the most highly concentrated and productive natural gas fields in North America, according to the BLM.
There, scientists found comparatively higher losses among the Brewer's sparrow and the sage sparrow, with the estimated rate of decline at six birds for every 10 additional wells per square kilometer.
But energy development did not affect all songbirds alike. For unknown reasons, the number of horned larks rose with well density in one gas field, and sage thrashers appeared unaffected by the industry, the study showed.
While habitat loss and alteration were cited as factors in the decline of sagebrush sparrow species, it was also possible that heavily developed areas opened the way for invading predators, like raccoons.
"One hypothesis is areas with human activities attract generalist predators," Chalfoun told Reuters.
Environmentalists like Erik Molvar of the Biodiversity Conservation Alliance said the BLM, which regulates oil and gas production on federal lands, should demand drilling methods that lessen damage to sagebrush.
An example is directional drilling, which requires fewer wells and a smaller footprint. A BLM official said the agency recognizes the impacts of energy development in environmental assessments for proposed projects.
BP America, which owns wells in the Jonah field, is said to be a leader in applying techniques like directional drilling.
"We can produce more energy without impacting as much habitat," Daren Beaudo, BP spokesman, said in a statement.
Encana Oil & Gas Inc. said geologic and economic factors drove that company to employ conventional methods like vertical drilling in its Jonah field operations. That method demands more wells and more traffic.
Spokesman Doug Hock said Encana did not dispute the data in the study, and was eyeing directional drilling for a new natural gas project in Wyoming that would allow for no more than 3,500 wells over 10 years.
"We're going to continue to monitor future studies as they are done for opportunities to look at further mitigation," he said.
(Editing by Steve Gorman and Cynthia Johnston)