THE BIRDS OF HELIGOLAND 335 



In the first case, this is effected by the peeling off of the inconspicu- 

 ously coloured envelopes of the barbs and barbicels of the winter 

 plumage, as has been treated of in further detail in Part I. of 

 this work, whereby the handsomer colour of the breeding plumage 

 concealed below is exposed. In the other case, however, this 

 change of coloration is effected in a manner which can only be 

 ascertained by the help of microscopic examination ; the black at 

 the lower margin of the white feathers making its appearance in 

 the form of a very fine, scarcely perceptible edge, which, gradually 

 widening, finally covers the whole surface of the feather. This 

 process starts at the black collar encircling the upper breast in 

 the winter plumage, and thence extends upwards to the last small 

 feathers of the chin. A similar alteration in colour from white to 

 black takes place in the same manner in the small black-headed 

 Gull (Larus minutus). 



The breeding range of this species appears to be almost exclu- 

 sively confined to Great Britain and its island groups, including 

 St. Kilda. Seebohm says that it nests occasionally in Holland, 

 more numerously in north-western France, and in solitary instances 

 in the south-west of Norway, to the last of which probably also 

 belong those individuals of this species which are met with in 

 Heligoland. Now, though these latter appear here only sparingly 

 from three to five at most on some days in March it is quite 

 probable, presupposing they are on the way to migrate to Norway, 

 that the birds breed in the latter country more numerously than 

 one suspects. 



147. Grey Wagtail [GRAUE BACHSTELZE]. 

 MOTACILLA SULPHUREA, Bechstein. 1 



Heligolandish : Giihl Lungen= Yellow Wagtail. 

 Motacilla sulphurea. Naumann, iii. 824. 

 Grey Wagtail. Dresser, iii. 251. 



Bergeronette jaune. Temminck, Manuel, i. 257, iii. 179. 



This extremely elegant and graceful bird should really occupy 

 the first place among all its congeners, for in it the ideal form of Wag- 

 tail reaches its highest expression. I shall ever keep fresh within 

 my memory a scene depicted before me during one pleasant hour 

 of summer on the west coast of the Scottish Highlands, in which 

 a family of these birds formed the living accessories. I was sitting 

 with my sketch-book in a narrow rock-valley of the picturesque 



1 Motacilla melanope (Pall.). 



