A: The swans that flew over you were probably mute swans, which ornithologist Philippe Jourde of the Service Etude du Patrimoine Naturel in France says "is the most common swan in that part of Europe."
"When flying, their wing beats produce loud, penetrating, rhythmic singing sounds — resembling 'vaou-vaou-vaou...", and audible one to two kilometers (a mile) away," emails Jourde. The loud wing sounds may help the birds stay in touch with one another, especially during migratory flights.
Moreover, contrary to their name, "mute swans are not mute," says Jourde. According to the Birds of Western Palearctic: calls are "often hoarse, explosively snorting, snoring, or grunting, usually with little of crooning, trumpeting, or honking quality of more vocal Cygnus [swans]." You can hear their calls by clicking here. Unfortunately, I couldn't find a recording of their wing beats, but are these calls the sound you heard?
On the other hand, they may have been whooper swans, migrating to breeding grounds in Scandinavia or Siberia. These 5-feet (1.5 m) long, 20-pound (10 kg) big birds fly laboriously but cruise at 50 mph (75 km/h). Or perhaps they were the smaller Bewick swans, heading for Siberia.
It's hard to say which of these three swan species flew over, but whoopers are certainly the noisiest. Birders liken whoopers' calls to a sound like 'gang-go-gang-go' or 'hoo-hoo-hoo.' Human imitation, though, does not come close. Only a recording begins to capture the bugle-like trills. Is this the sound you heard?
You no doubt also heard their wings beating. Whooper-swan "wings produce a musical sound when flying," say French ornithologists of the Oiseaux.net (meaning 'birds'). Moreover, their varied, modulated song sounds like a "husky, distant bell."
Courting
mute swans. Photo courtesy of Bowenpan and Wikipedia.By the way, whoopers sing while courting, and mate for life. They dance with their necks to the tune of "loud bursts of trumpeting," says Birds of Britain. A pair faces each other with lifted, quivering wings, half open. Each bends the long thin neck into a graceful curve, heads almost touching, then lifts and straightens the neck, in time with the other, and repeats the movement many times.
Let us know who won the bet!
Further Reading (and Listening):Whooper Swan best audio, interesting info, Oiseaux.net Mute swan, hear their calls, Cornell University Mute swan, Animal diversity web, University of Michigan Whooper Swan Migration, USGS The Birds of the Western Palearctic, Robert Gillmor et al Whooper Swan good audio, whatBird.com Bewick's Swan, good audio, RSPB Whooper flight speeds, National Environmental Research Institute, Denmark, Netherlands Institute of Ecology |
Melissa T., Dayton, Nevada, USA
Richard, Port Washington, New York, USA
(Answered July 2, 2007)