THE GREY WAGTAIL. 309 



tipped and margined with white, which forms a white spot, 

 and two longitudinal white streaks on the closed wing. The 

 tail (which is very long) has the outer feather, the inner web 

 of the second, and a streak on the inner web of the third, 

 white, and all the rest black. The bill and gape are black ; 

 the feet dusky brown, with the exception of the joint of the 

 tarsus, which is yellowish. 



In the breeding season, the colours of the female are nearly 

 the same, only a good deal paler and less distinct, the yellow 

 being whiter, and the grey having a shade of black, while in 

 the male it inclines more to blue. In winter, the male, in a 

 great measure, loses its distinguishing colours. The black on 

 the throat gives place to pale greyish-white, and the whole 

 under part becomes very pale j the female also loses the black 

 on the chin, which is, indeed, never so pure and conspicuous 

 as that on the male. 



These changes of colour indicate an adaptation to the tem- 

 perature of the season, so that the migration of these birds 

 may, like that of the pied wagtails, be regarded chiefly as a 

 migration for food : indeed, the want of food in the polar 

 climates may be considered as the grand operating cause in 

 all equatorial migrations. 



The grey wagtail leaves the southern parts of the country 

 (in which it is called the winter wagtail) about February or 

 the early part of March, the cause which changes the plumage 

 appearing to operate simultaneously in prompting the migra- 

 tion, as the sexes resemble each other as long as they remain 

 in the south. Many of them halt by the upland streams in 

 the central and northern parts of England ; but others pass 

 into Scotland, where they penetrate to a considerable distance 

 north, although, as they keep to more retired situations, they 

 are not so often seen in proportion to their numbers as the 

 pied wagtails. They are also more confined to the clear 

 streams in the open wastes, where they feed upon water-flies, 



