Endangered Species: Sage-Grouse Penned-In By Power Lines

Threatened-species the greater sage-grouse has reached certain limits: It won't cross power lines, and its species' genetic diversity is therefore damaged by this. That is, researchers with the University of Washington who studied greater sage-grouse populations in flat, prairie-defined Eastern Washington recently published their findings about this in the journal Landscape Ecology.

The sage-grouse is an iconic ground-dwelling bird that spans 11 western states. As a result of its recent population decline, researchers are investigating how landscape features limit the species' distribution and gene flow.

The researchers' study explains that current and future power-line development across the Columbia River Plateau could further weaken the species, which is currently considered to be a threatened species in Washington state, and is up for listing under the federal Endangered Species Act. A decision on the latter may happen by the end of September.

"With only a fraction of pre-settlement habitat left in the state for this species, it's key that all of that habitat be connected in order for the population to be viable in the future," Andrew Shirk, lead author and research scientist with the University of Washington's Climate Impacts Group, said in a statement. "The best way to keep sage-grouse genetically viable is to keep the population connected across all the available habitat. Habitat connectivity is also essential for the species to shift its range over time as climate change alters the distribution of its habitat."

For their study, researchers looked specifically at the Washington population of approximately 1,000 of these large birds that depend on sagebrush plants for food and shelter. They looked at the three distinct groups that live in the the Columbia Plateau, the statement said.

The team developed a model for the birds' movement using genetic information from feathers and blood and observations of about 70 breeding areas. According to their study, in order to maintain genetic diversity, the birds must be able to travel among sub-populations to prevent inbreeding. When collaborating all their data, the team was able to produce a more accurate model for prediciting how sage-grouse will move across the landscape under futuer scenarios. They also found that transmission towers and power lines act as barriers that limit the birds' movement between habitats, since they avoid them at all cause due to predatory birds lurking on the lines overhead or the accidental stumble into one of the poles, according to the statement.

"The power-line transmission corridor barriers were very strong and somewhat unexpected," Samuel Cushman, co-author and research landscape ecologist with the U.S. Forest Service, said in the statement. "These corridors crisscross the landscape throughout the range of the sage-grouse and they appear to be very impactful to the population's connectivity."

The researchers found that two of the sub-populations in Washington are only three miles apart. However, they have to cross rivers, a major highway, steep terrain and fruit orchards to reach each other.

"We really want to recover these populations so they're not only sustainable, but also healthy," said Michael Schroeder, a research scientist with the Washington Department of Fish and Wildlife who has worked with sage-grouse for about 35 years, in the release. "We want to make these functioning landscapes and not always have to think about first-aid solutions for these populations."

While this new model is based on Washington birds and data and can't be directly extrapolated to other states' grouse populations, authors say that the negative impact of transmission lines on habitat connectivity is likely to impact all of the sage-grouse in the West, said the release.

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