THE BIEDS OF HELIGOLAND 339 



150. Black-headed Wagtail [SCHWARZKOPFIGE 

 BACHSTELZE]. 



MOTACILLA MELANOCEPHALA, Lichtenstein. 



Heligolandish : Swart-hoaded Giihlblabber=Zac/c-Aeade( Wagtail. 



Motacilla melanocephala. Naumann, xiii. ; Blasius, Nachtrage, 125. 

 Black-headed Wagtail. Dresser, melanocephala y iii. 273 ; viridis, 269. 

 Motacilla melanocephala. Temminck, Manuel, iv. 623. 



From the examples of this species to be found in Heligoland 

 annually during the spring migration it is impossible to divide the 

 yellow Wagtails without white eye-streak into grey and black-headed 

 sub-species, for among the males one meets with every gradation 

 of head colouring, from a dark blue slate grey to a pure brilliant 

 black. In the latter individuals, at the time of their arrival, 

 the whole of the crown of the head down to the neck', the sides of 

 the head and neck as far as the back, are of a pure brilliant black. 

 The occiput is covered by a mixture of broadly barbed, slaty-black, 

 more- or less-worn feathers of the winter plumage, and silky 

 brilliant pure black feathers which have been renovated by altera- 

 tion of colour. This can be very well seen if, under a moderate 

 magnifying power, one passes a piece of white paper under some of 

 the separate feathers. Undoubtedly all the feathers of the hinder 

 part of the neck have undergone this re-coloration by the time 

 the birds have reached their nesting stations, so that the birds are 

 then of a uniform black from the forehead down to the back. 



Beautiful black examples of this kind are, however, met with 

 only in solitary instances, and almost always among the earliest 

 arrivals of the spring migration, these being doubtless the oldest 

 males. In such birds the foreneck is at that time also pure 

 yellow up to the last small feathers on the bill ; a white chin I 

 have observed only in the case of later arrivals, these being birds 

 of less age, in which the crown of the head was invariably 

 of lighter or darker slaty-blackish grey, and in which the change 

 of colour to a pure black had made only a slight advance from 

 the forehead. 



It is surprising that investigators who visited the northern 

 breeding stations of this species appear not to have met with old 

 black-headed males like these, since their regular occurrence in 

 Heligoland during the spring migration proves that they must be 

 represented in the former districts also ; further, it seems unintel- 

 ligible why they should.be resident in northern and southern 



