Mute swans have a familiar pose with neck curved back and wings half raised. Although it is a beautiful pose, it is a threat display called busking. Although these swans are named mute swans, they are not mute. they make a variety of sounds including grunting, hoarse whistling, and snorting noises, especially in communicating with their cygnets (off-spring). They usually hiss at predators trying to enter their territory.