The male sage grouse has air sacs that, when not inflated, lie hidden beneath the grouse' s neck feathers  During its spring courtship ritual, the male sage grouse inflates these air sacs and displays them to the female sage grouse
Some scientists hypothesize that this courtship ritual serves as a means for female sage grouse to select healthy mates
Male sage grouse are prone to parasitic infections that exhibit symptoms visible on the birds' air sacs.