Male prairie chickens gather at dawn on communal display grounds called leks, where they stomp their feet rapidly, inflate bright orange air sacs on either side of their neck into pulsing balloons, and raise stiff feather pinnae above their heads like little horns while emitting a deep, hollow booming sound that carries across the grassland. They spread their wings low, fan their pointed tail feathers upright, and spin, strut, and occasionally leap or clash with rival males in short skirmishes, all while females watch from the sidelines and select a mate based on the vigor and consistency of his performance.