This April 2011 file photo provided by Colorado Parks and Wildlife shows a male and female Gunnison sage grouse near Gunnison, Colo. New research could have implications for sheep and cattle grazing in the habitat of the ground-dwelling bird that environmentalists are trying to protect across the Rocky Mountain region. A study published in the December issue of Wildlife Biology suggests grass height can have a big influence on the nesting success of the greater-sage grouse. (AP Photo/Colorado Parks and Wildlife, Mike Danzenbaker, File)
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