MOTACILLA FLAVA 149 



superciliary stripe, little or no white on the chin and none at all on 

 the throat. 



(b) M. cinereocapilla : with a similarly coloured crown, generally 

 without a white superciliary stripe, but sometimes with a slight one, 

 chiefly behind the eye, and with a distinct white chin aud throat. 



(c) M. borealis : with a darker slate-coloured crown, without any 

 superciliary stripe, and with little or no white on the chin, and none at 

 all on the throat. 



(d) M. melanocephala : with a perfectly black crown, and without 

 any superciliary stripe, or any white on the chin and throat. 



(e) M. rayi : with a yellowish-green crown, a yellow superciliary 

 stripe, and no white on the chin and throat. 



It is not without considerable hesitation that I admit all these 

 forms to full specific rank, some, if not all of them, appearing to me 

 to be merely subspecies, or local forms, and some authors, indeed, go 

 so far as to lump them all together under M. flava, Linn. According 

 to excellent authorities, however, there are good reasons for specific 

 separation or sub-division, apart from the variation of plumage 

 colouring and marking, and some careful observers profess to be able 

 to distinguish a difference between the respective notes and habits 

 of the various forms, as well as between the relative dates of their 

 arrival and departure, and even, in one or two cases, in their structural 

 parts. According to some good ornithologists also, the various forms 

 have different breeding areas, and should this fact be established for a 

 certainty, it would no doubt constitute a strong argument in favour of 

 specific distinction. So far, however, as our present knowledge goes, 

 it is diflicult to arrive at a definite conclusion on the matter, and 

 we must be content to wait until further research may throw more 

 light upon the subject. 



The fact of the young birds of the various forms being practically 

 indistinguishable one from the other greatly adds to the difficulty of 

 identification, and it is by no means an uncommon occurrence to find 

 birds, not fully adult which show, in a greater or less degree, what 

 are considered to be the characteristic features of two different forms, 

 thus rendering their identification an absolute impossibility. 



The Blue-headed Wagtail is a bird of regular passage throughout 

 the greater part of the Tunisian Eegency, being particularly plentiful 

 during the spring migration, when the species may be noticed, in 

 greater or lesser numbers, from about March 20th until the end of 



