10 BULLETIN 19 7, UNITED STATES NATIONAL MUSEUM 



about on the ground and is quite often heard from birds on passage^ 

 Indeed, it has very little if any sexual or territorial significance, and 

 one of the major functions served by the song of most birds, that of 

 advertisement to possible mates in spring, seems here to be discharged 

 by the tschizzik note, which is uttered persistently from such points 

 of vantage as roofs, walls, or rocks. 



Field marks. — The white wagtail and the other races of Motacilla 

 alba are very easily recognized, though the separation of the races 

 may be difficult or in some plumages impossible in the field. They are 

 small, slim, long-tailed birds (total length about 7 inches), with a pied 

 pattern of gray, white, and black, spending much of their time on the 

 ground, where they walk and run actively, constantly moving the tail 

 up and dow]i in a very characteristic manner, and the head back- 

 ward and forward. The flight is equally characteristic, strongly un- 

 dulating, in a succession of long curves with the wings closed at brief 

 intervals for perceptibly longer than in the case of most small passer- 

 ines of similar size. The note tschizzik, which is freely used in flight, 

 is also distinctive. 



In the white wagtail the mantle and rump are clear pale gray, 

 nape and hind part of crown black, forehead, front of crown, sides of 

 face, and belly white. In summer the whole throat and breast are 

 black, but in winter plumage the throat is white bounded by a horse- 

 shoe-shaped black bib. The wings and tail are blackish, with 

 double white wing bar and white outer tail feathers. In the female 

 the gray is rather duller than in the male, and young birds in the 

 Juvenal plumage are altogether duller and more uniformly grayish 

 without the strong blacks and whites, as described under "Plumages." 

 Differences from M. a. ocularis and M. a. lugens, the other two races on 

 the American list, are mentioned in the accounts of those forms. 



Enemies. — The white wagtail falls a victim at times to various hawks, 

 and in the northern regions the merlin (pigeon hawk) is evidently its 

 chief avian enemy. Greaves (1941) mentions (European) sparrow 

 hawks and peregrine falcons attacking birds at roosts in Egypt. Four- 

 footed marauders, such as rats and weasels, sometimes take toll of the 

 nestlings, and owing to the association with human habitations which 

 has already been stressed the domestic cat must be accounted an im- 

 portant enemy. Hantzsch (1905) particularly mentions prowling cats 

 as special enemies about the farms and settlements of Iceland. In 

 continental Europe the cuckoo frequently lays its eggs in nests of the 

 white wagtail, and as this means that the wagtails can rear no brood 

 of their own, since the rightful young ones are ejected from the nest 

 by the young cuckoo, the cuckoo must be included in the list of enemies. 



A list of invertebrate parasites is given by Niethammer (1937) , and 

 the same author states that not a few nestlings appear to succumb to the 

 attacks of the larvae of the fly Protocalliphora caerulea. 



