Study eyes powerlines as factor in sage grouse decline

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Greater sage-grouse avoid powerlines, and the poles are used by perching raptors that target sage grouse nests. Photo via USGS.

Another piece in the sage grouse puzzle …

Staff Report

FRISCO — After closely studying a greater sage-grouse subpopulation on the Columbia Plateau in eastern Washington, wildlife biologists said that power lines may be a greater factor in habitat fragmentation than previously believed.

The new study found that transmission lines from hydroelectric dams and wind turbines affect greater sage grouse habitat by isolating fragile populations and limiting movement. The was published online this summer in the journal Landscape Ecology.

“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,” said lead author Andrew Shirk, a research scientist with the University of Washington’s Climate Impacts Group.

Shirk said the habitat connectivity is the best way to keep greater sage-grouse populations genetically healthy.

“Habitat connectivity is also essential for the species to shift its range over time as climate change alters the distribution of its habitat,” he said.

Power lines and future development across the Columbia Plateau could further weaken the species, which is listed as threatened in Washington state. The entire U.S. population that spans 11 western states is up for listing under the federal Endangered Species Act and a decision on whether to officially designate the population as endangered is expected by the end of September.

On the Columbia Plateau, stretching from the cities of Wenatchee, Ellensburg and Yakima on the western edge to of Moses Lake in the east, Interstate 90 runs directly through their home range, and the birds have lost more than 90 percent of their historic habitat to roads, development, wheat fields and power operations.

Using genetic data collected from feathers and blood, and by observing whether birds were present in about 70 different breeding areas, the team developed a model for how birds move and to predict how they will move in the future. The animals must be able to travel among sub-populations to prevent inbreeding, which causes a loss of genetic diversity across the entire population.

“The power-line transmission corridor barriers were very strong and somewhat unexpected,” said co-author Samuel Cushman, a research landscape ecologist with the U.S. Forest Service Rocky Mountain Research Station. “These corridors crisscross the landscape throughout the range of the sage grouse and they appear to be very impactful to the population’s connectivity.”

Researchers say the birds avoid the tall transmission towers and power lines, which stand out in their usually expansive landscape. Some grouse have collided with the towers, and the structures attract predator birds that perch on the lines, targeting grouse eggs or even the birds themselves.

In Washington, two of the sub-populations are only 3 miles apart, but they have to cross rivers, a major highway, steep terrain and fruit orchards to reach each other. Restoring more natural habitat between the groups is key to their survival.

“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 grouse for about 35 years. “We want to make these functioning landscapes and not always have to think about first-aid solutions for these populations.”

The new model is based on Washington birds and data and can’t be directly extrapolated to other states’ grouse populations. But the study’s authors say the negative impact of transmission lines on habitat connectivity is a robust result and they believe it is likely to impact all of the sage grouse in the West.

This research was funded by the U.S. Fish and Wildlife Service’s Great Northern Landscape Conservation Cooperative and the U.S. Bureau of Land Management. The paper’s other co-author is Leslie Robb, an independent biologist with the Washington Wildlife Habitat Connectivity Working Group.

A copy of the paper can be downloaded here: http://www.treesearch.fs.fed.us/pubs/48846.

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