About 170 greater sage grouse gather on Wes McStay’s ranch in northwestern Colorado. They're here to mate in an open field of recently-planted rye.
Biologists call such a gathering a lek, where male grouse perform an elaborate mating dance that involves inflating two yellow air sacs in their chests and then releasing the air with a bubbling pop.
The national sage grouse coordinator for the U.S. Fish and Wildlife Service watches the spectacle, her gloved hands holding binoculars tightly to her face.