COLOUR-CHANGES WITHOUT MOULTING 153 



which in the winter plumage were rigid, and not in contact with 

 each other, as a result of this peeling off become thinner and more 

 closely opposed to each other, thereby imparting to the whole of 

 the feathers a glossy, silky appearance. Further, the feathers, 

 which by the end of the winter were worn irregularly, and blunted 

 at the tips, after this change of colour, again have their margins 

 completed, and their tips beautifully and evenly rounded off, so 

 that they are in all respects like perfectly new feathers, such as 

 would be produced by moulting. This process may be observed 

 very distinctly in the feathers of the back of the Pied Wagtail. In 

 this bird the colour of the winter plumage is a dusky slate-grey, 

 and devoid of gloss, but after the completion of the breeding plumage 

 it becomes deep black and of silky brilliance. This black colour 

 first makes its appearance as a narrow black border at the tips of 

 the feathers, which soon spreads over their whole surface. 



The number of species in which this change from the winter 

 plumage to the more attractive breeding garb is effected, in the 

 manner last described, seems to be fewer in so far at least as 

 the birds occurring in Heligoland are concerned than that of 

 the species in which this transformation is carried out by the 

 simple falling off of the dull-coloured edges of the barbs of the 

 feathers, as previously explained. 



The last and most wonderful process in the colour changes of 

 the plumage of birds, not attended by a renewal of the feathers 

 themselves, consists in an actual, complete, and very striking change 

 in the colour of the feathers, without such alteration being brought 

 about, or even assisted, by any changes in their texture. 



As illustrating the climax of this process we may probaljy point 

 to the change from a pure snow-white to an intense glossy black or 

 blackish brown. The first of these transformations is displayed in 

 portions of the head and neck of the Little Gull, the fore-neck and 

 upper breast of the White and Pied Wagtails, the breast of the 

 Dunlin, and others. The latter change, from white to blackish 

 brown, is observed in the necks and heads of the Guillemots, of 

 the Razorbill, and undoubtedly also of the Little Auk. 



In the first-named species the change of colour from white to 

 black is brought about in the following manner: commencing 

 below, at what afterwards marks the line of separation between the 

 black and white markings, the colour appears at first in scarcely 

 perceptible dots of pure black at the extreme tips of the separate 

 barbs of each feather the lower portion of the edge being the first 

 to be affected, and thus acquiring a narrow border composed of 

 extremely fine black specks; by degrees these edges increase in 

 breadth until the black colour, extending towards the roots of 



