Images from On a wing and a prayerback to the article
by Louise Swift (L) and Rob Bennetts (R). Courtesy Jessica Young
The greater sage grouse, left, is about a third bigger than the Gunnison sage grouse. The two have different kinds of feathers and produce different sound using their yellow air sacs, and the Gunnison has a more elaborate and more colorful filoplume, which it tosses over its head during display. In March, the National Audubon Society named the Gunnison sage grouse one of American's 10 most endangered birds. It numbers around 5,000, while the greater numbers around 140,000.