This behavior, which can be agonistic or part of courtship, is described as follows by Birds of North America Online: "Male holds head and tail and 2 rows of feathers on crown ('horns') erect, inflates neck; begins beating bill slowly at first against neck, forcing air out of feathers, causing bubbles to appear in water; beating intensifies toward end of display with concomitant movement of tail over back and head moved slightly forward over water; low belching sound uttered at end."