Swans absolutely make noise, producing a complex array of sounds that serve a variety of communication needs. The sounds they make range from the deep, powerful calls of North American species to the quieter vocalizations and distinctive mechanical noises of the common European swan. This variation in acoustics is largely dependent on the species, with some swans having evolved specialized vocal anatomy for long-distance signaling, while others rely more on non-vocal methods to express themselves.
The Vocalizations of True Swans
The most vocally expressive swans, such as the Trumpeter Swan and the Tundra Swan, are known for their loud, resonant calls that carry over great distances. The Trumpeter Swan produces a deep, sonorous sound often described as a distinctive bugle or trumpet call, which is typically emphasized on the second syllable, sounding like an “oh-OH”. These powerful vocalizations are achieved through a specialized anatomical feature: a long trachea that is coiled within the sternum.
This extended and convoluted windpipe acts like a natural brass instrument, amplifying and deepening the sound produced. The calls of the Tundra Swan are also bugling but tend to be higher-pitched and smoother compared to the Trumpeter Swan’s deeper tone. These loud calls are primarily used as contact signals to maintain flock cohesion or to communicate territorial boundaries across vast, open waterways.
The Mute Swan Misconception
The widespread belief that swans are silent stems mainly from the Mute Swan, the species most commonly found in parks and waterways across Europe and North America. Despite its name, the Mute Swan is not actually silent, though its vocal repertoire is significantly less resonant than that of its North American relatives. This species lacks the elaborate tracheal loop necessary to produce the loud, carrying bugle call.
Mute Swans communicate using softer, less projected sounds typically used for close-range interactions. These include soft snorts, short grunts, and a low, throaty rumble often heard between mates or when the bird is content. When threatened, they produce an explosive snorting or a sharp, forceful hiss, which is primarily defensive.
Sounds Made by Movement
Beyond vocalizations, swans generate noise simply through movement, most notably from their wings. The Mute Swan’s large wing feathers create a loud, rhythmic sound during flight, often described as a throbbing, humming, or whistling noise. This distinctive acoustic signature is so pronounced that it can sometimes be heard from over a mile away, earning it the poetic name of the “song of the swan.”
This acoustic output serves an important communicative function, essentially replacing the loud contact calls of other species. The sound acts as an audible signal, letting flock members know where the bird is located, especially during migratory flight or when landing. Non-vocal sounds also occur when the birds slap the water with their webbed feet, which can be an aggressive signal to an intruder or a form of communication during takeoff.
Context: Why Swans Vocalize
Swan sounds, both vocal and mechanical, are tied directly to specific behavioral contexts. The most aggressive sound is the loud, sudden hiss, which is a clear warning signal given when a swan, particularly one guarding a nest or cygnets, feels its territory is being encroached upon. This defensive posture is often combined with a physical display, like arching the wings, to maximize the threat.
The deep bugling and trumpeting calls of species like the Trumpeter Swan serve as an acoustic marker for territorial defense and help family groups maintain contact over great distances during foraging or migration. Softer, more intimate sounds are used for pair bonding and greeting rituals, such as the snoring sound mates may use upon reuniting, or the soft whistles given by cygnets as contact calls to their parents. These varied noises and movements collectively form a rich communication system.