The second photo is a close-up of a male or cock Greater Sage-Grouse as he performs his
ritual strut. Males have an esophageal pouch, which is inflated by the
bird as it sucks in air. Once the pouch is inflated, it looks like a
greenish-yellow balloon. As the cock steps forward, he brushes his wing
feathers against his stiff breast feathers, making a swishing sound.
Then the male stops and abruptly releases the trapped air, Êemitting a
low pitched "blooping" sound.