It’s a sweltering summer day in central Montana. Here, in the heart of Big Sky country, no matter how hot it gets, blue jeans and cowboy boots are the norm, to protect against the whipping wind and the threat of thunderheads that can materialize without warning on the horizon.

Rancher Bill Milton surveys his land with wildlife biologist Dan Casey from a bumpy dirt road etched into the mottled green and gold landscape, 50 miles outside of Billings. Rolling through the land in Casey’s Prius, we’re on the western margin of the northern Great Plains, where shortgrass prairie once dominated the landscape. Casey points out an apple-sized bird on the right hand of the road.

It’s a chestnut-collared longspur, whose males sport