476 



MOTACILLIB^. 



tinged with yellow, cspeciall_y on the lower parts ; across the fore 

 neck a broad crescent of black ; remainder of under surface of body 

 pure white, with a shade of grey on the breast and ashy on the sides 

 of the body ; axillaries pure white ; under wing-covcrts also white ; 

 quills dusky brown below, with a great deal of white along the inner 

 web. Total length 7'5 inches, culmen 0*G, wing3'6, tail 3-7, tarsus 0-95. 

 Obs. There is a great deal of diifcrence in the amount of olive on 

 the back of the winter-plumagcd birds, and also in the extent of 

 yellow on the eyebrow, face, and throat. The wings are those of the 

 first plumage, but with much more white on the coverts and a larger 

 extent of white along the inner web. No sooner is the winter dress 

 completed than the approaching spring plumage begins to assert 

 itself and the head commences to turn black, the black of the back 

 appearing later. Thus Capt. Blakistou's collection contains specimens 

 procured in October, one of which has a great deal of black on the 

 head, while the other has the head uniform with the back ; the latter 

 I consider to be a bird of the second brood, and therefore later in 

 showing the approach of mature plumage. Along with the black on 

 the head the black edges to the feathers of the throat show a cor- 

 responding development. These changes of plumage are perfectly 

 analogous to those undergone by the common Pied WagtaU of 

 Europe (M. luguhr'is). 



Wing of M. lugcns, showing the commencement of the white quills. 



The breeding-plumage is thoroughly assumed in the first spring, 

 the black gradually extending on the throat, but not occupying the 

 chin, while the whole back excepting the forehead becomes black, 

 the quills and tail-feathers beuuj retained (though it would seem as 

 if in some specimens the long inner secondaries were renewed in the 

 spring, reappearing as black as the back, with broad white margins). 

 This process of change, which is abundantly illustrated in Capt, 

 Blakiston's series, explains how it is that some black-backed males 



