National Geographic : 1980 Jan
(facingpage). The cock takes on his rivals in combat-partreal, part ritual-fora piece of turf, where he dances and displays to attract a mate. His characteristicbooming call is amplified by inflatable neck sacs. From the sidelines the watching hens approach,favoring dominant males. Other birds are drop-in visitors. The Swainson's hawk (right),pausingduring his migration,stretches on a fence post while huntingfor small rodents and grasshoppers.