THE SWANS 181 



young utter a piping-note. Lastly, when the great bird is on the 

 wing, a creaking noise, which is not vocal, but due to friction of the 

 quills, is audible with each wing stroke, and can be heard quite 

 easily half a mile away, while it is distinguishable by a good ear at 

 double that distance. 1 



Even when all these sounds are taken into consideration, the 

 fact remains that the domestic swan is essentially a silent bird. On 

 the other hand, both the whooper and Bewick's swan are decidedly 

 noisy, and their loud call-notes are most exhilarating, as the herd is 

 seen winging their way over the mud-flats of some estuary, their 

 snow-white plumage and black feet showing up splendidly against 

 the gloomy sky. This difference of habit is based on striking 

 distinctions in the anatomy of the three birds. In the fourth edition 

 of Yarrell (iv. pp. 314, 320, 321, and 329) will be found figures 

 illustrating the windpipe and breastbones of all three species. Here 

 it is sufficient to remark that while in the mute-swan the keel of 

 the breastbone is single, as in most birds, and the windpipe short, in 

 both the other species there is a cavity in the sternum, and the 

 windpipe passes along almost the full length of it between the walls 

 before returning, and passing upward into the body cavity, where it 

 is connected with the lungs. There are further differences between 

 the form of the trachea in the whooper and Bewick's swan, which 

 are illustrated in the figures referred to. 



The call-note of the whooper is generally described as a loud 

 " whoo-whoo " or " whoop, whoop" repeated several times in succession, 

 with a slight pause between each double call. Patten compares it to 

 a full-toned whistle, Lilford to a bugle-call, and Naumann to the 

 sound of a trombone. The last-named writer notes that the depth of 

 tone is variable, and differs considerably in individuals and probably 

 also in the sexes. He writes the sound as "klung" The trumpet-like 

 notes of a large flock, mixed with the regular swish of the great wings, 



1 Stevenson also describes a "strange yapping note" like the bark of a small dog, used to 

 entice the young from the nest. 



