The tail is distinctive: the two central feathers lose their barbs along a section of shaft during preening and normal wear, leaving bare wire ending in an intact racquet. The bird swings this from side to side in a slow, deliberate arc while perched.
Troy Murphy tested the function in 2006 and 2007 with wild Nicaraguan birds. Wagging increased in the presence of a predator model and was performed by solitary birds as readily as by birds with a partner nearby, which argues against a signal aimed at mates or rivals. The pattern fits pursuit-deterrent signalling: an honest announcement that the ambush has failed, which is in the interest of both parties.
The common account that motmots strip the barbs deliberately to make racquets is doubtful. The barbs along that section are weakly attached and come away through ordinary preening and abrasion, so the shape emerges without a plucking behaviour being required.