188 THE SWANS 



seen during the winter months in large herds. The differences in the 

 notes of the two species have already been pointed out, and the 

 distribution of the black and yellow on the bill is best grasped by 

 referring to the illustrations. On the tundra of the islands of North 

 Russia and Siberia there is but little vegetation available for nest- 

 building but moss, and Mr. Trevor-Battye describes a nest found by 

 him on Kolguev as a mound 2 feet high, consisting almost entirely of 

 this material, mixed with lichens and grass. 1 On these open plains they 

 are often conspicuous, standing some 22 inches high. As the male 

 bird is said to remain close to the nest while the female incubates, 

 in all probability the incubation habits of all three birds are similar. 

 Nine well authenticated eggs are smaller than whoopers', averaging 

 4-07x2-65 in. [103*6 x67'3 mm.]. The duration of the incubation 

 period is unknown. In disposition Bewick's swan is timid and gentle, 

 and has little of the domineering and combative nature of the 

 whooper, never molesting the smaller waterfowl, even when confined 

 with them in a restricted space. The surface-feeding ducks in parti- 

 cular are apt to take advantage of the presence of the larger birds, 

 feeding on the weeds torn up by them and lying on the surface of 

 the water. 



Both Bewick's swan and the whooper sometimes show traces 

 of reddish-brown colouring on the head and upper neck. When 

 chemically tested this has been shown to be due to peroxide of iron, 2 

 and is due to the bird feeding in water charged with iron deposits. 

 A whooper which I watched for some time in June 1912 on a shallow 

 pool among the hills in Iceland, had the head and neck deeply stained 

 with peat and suspended iron, producing a most extraordinary effect 

 at a little distance. No doubt most of this would be washed off, but 

 the iron tends to stain the feathers permanently. 



1 Nordenskiold gives a somewhat similar account, adding that the moss is plucked from 

 a distance of about six feet from the nest, forming a sort of moat round it. 

 1 Stevenson, Birds of Norfolk, in. p. 78. 



