160 THE BIRDS OF HELIGOLAND 



In the head, neck, upper breast, and sides of the breast, the 

 change commences by the disappearance of the grey colour of the 

 winter plumage ; the feathers become white, and each at the same 

 time acquires a small black streak in the line of its shaft ; the latter 

 extends towards the tips of the feather in the form of lanceolate 

 or sagittal markings, and in the large feathers on the sides of the 

 breast develops into barred markings. The feathers on the middle 

 of the breast, as well as those of the belly, which acquire no 

 black markings, likewise share in the general alteration of colour, 

 in so far as they become more purely snow-white. It is well known 

 that the feet, and the root of the lower mandible also, during the 

 alteration of the colour of the plumage, pass from the dull brick-red 

 of the winter plumage to a beautiful pure vermilion red. 



To explain the origin and course of development of the trans- 

 verse bars of the long posterior flight-feathers of this species would 

 be as difficult, if not more so, than to account for the first appear- 

 ance of the black colour at the lower edges of the white neck- 

 feathers of the Little Gull. If we are unable to assume in the latter 

 case that the colouring matter passes unobserved from the body 

 through the shafts of the feathers to the extreme tips of the bars, and 

 thence spreads visibly upwards over the whole surface of the feathers, 

 we are still less justified in adopting such a view in regard to the 

 transverse bars which mark the feathers of the Kedshank ; for the 

 barbs of these feathers are placed much more at acute angles to 

 the shafts than the dark transverse bars, so that the former are 

 crossed by the latter in many ways, and display in the lines of their 

 length several gaps which are not marked by the dark colour. We 

 may therefore well ask how the dark colouring matter could leap 

 over these intervening gaps to get to the place of its destination. 



In the species hitherto discussed we have traced the course of 

 the alteration of colour from the winter to the breeding plumage, as 

 this proceeds in all old birds which are capable of producing a 

 brood. We may accordingly regard this as the normal phase of 

 the phenomenon. In establishing this conclusion, we have however 

 by no means come to the end of this interesting subject, for many 

 cases occur in which the colour of the early plumage of young birds 

 is also more or less completely changed to that of the breeding 

 plumage of old individuals. Under these conditions, however, we 

 can only regard the process as an exceptional case of assistance or 

 protection, which, as I have grounds for believing, does not affect all 

 the individuals of a species which are of the same age, but only 

 such as are specially strong. What, however, particularly leads one 

 to regard the phenomenon as abnormal is, on the one hand, the 

 fact that a partial alteration of the colour of young birds takes place 



