138 OBSERVATIONS ON MOTACILLA ALBA, LINN., 



numbers of young- dukhunensis on their early autumnal arrival, 

 but never saw this yellow tinge so conspicuous on young alba 

 on any single head. This difference alone is conclusive, even 

 if the adult birds had exactly the same wing-coverts. A simi- 

 lar difference is observable in the young of the two Budytes, 

 rayi and flava, one being dull fulvous white, and the other 

 white. This goes strongly against the lately fashionable 

 theory, as baseless as it was fashionable, that all the species cf 

 Budytes are varieties of one, viz., flava. The idea that melano- 

 cephala, or cinereocapilla, or even rayi, might have been the 

 source, appears not to have occurred. And what about the 

 long-billed and most distinct B. taivanus ? It was confounded 

 with rayi ; but a glance at it forbids the idea, its structural 

 difference being so decided. 



5. Why should M. alba and M. dukhunensis, if the same 

 bird, differ, since other Wagtails, common to both Continents, 

 as B. melanocephala, and B. cinereocapilla, do not differ ? 

 My observations lead me to the conclusion that the black and 

 white Wagtails are remarkably constant in their characteristics, 

 and they are about the last birds in which I should expect 

 Continental variation. Difference of longitude, no more than 

 difference of latitude, can affect the small insectivorous migrants. 

 In the present case I would not consent to identity until the 

 white wing-coverts are as common in Europe as in India, and 

 until the young in both Continents were alike. A slight differ- 

 ence is often of very great importance, and a constant differ- 

 ence, however slight, is against identity, and is of the same value 

 as if the differences were numerous and most marked. To the 

 ornithologist it should be so. 



Take two Buntings that Mr. Dresser keeps distinct, and I 

 think justly so- — E. cia and E stracheyi. The differences are 

 not so well marked as in the two Wagtails. In the latter we 

 have not only adult difference and geographical difference, 

 but we have, too, a juvenile difference. I don't see what more 

 is required for specific distinctness. The difference in the 

 juvenile plumage is a very strong one, stronger than the wing- 

 coverts of the adults. It cannot be set aside. 



I think we should also take great notice of the much superior 

 grey of dukhunensis at all times. Alba is much more dusky. 



I forget whether adult alba is tinged with straw colour about 

 the head in winter. Dukhunensis never is. 



This question leads to another: European examples of 

 B. flava don't agree as regards the head with those of India. 

 The grey of the crown of the former is darker, and there is an 

 amount of very dark grey on the cheek, mixed with a small 

 white streak or two, which dark grey we do not see in the Indian 



