110 GRALL.E. 



as that the young leaves are secure from the frost by the 

 protection of the old ones. 



The analogy would lead us to suppose that the northern 

 birds too should have two sets of feathers upon them during 

 the inclement season, one of which begins to be produced in 

 each year after the breeding is over ; and as the new ones 

 grow, the old ones fade and dry by slow degrees ; and as they 

 dry their colours fade, even to white where the cold is severe 

 and sufficiently prolonged. That has been already hinted at 

 in the case of the ptarmigan, the snow-bunting, and several 

 others ; and observation proves that while the upper fea- 

 thers are fading and losing their colour, new ones are grow- 

 ing, which are more coloured in their rudimental stages, and 

 which become deeper and deeper in the tint as they become 

 more produced, and ultimately appear between and mottle 

 the paler livery which the bird has worn in the winter. 

 And though the change can be traced, in the very same fea- 

 ther, from the dark tint to the pale while the winter is 

 becoming colder, there is no evidence that the same feather 

 which was once pale becomes darker by more seasonal action, 

 though a seasonal bloom may come upon some of fhe feathers, 

 just as sexual feathers are produced and decay upon some 

 birds, with little or no reference to the general change of the 

 plumage. 



Upon those resident birds that undergo seasonal changes 

 in their whole plumage, there is, therefore, an upper plumage 

 which is fading, and an under plumage which is growing, 

 during the winter, just as there is upon hill cattle one coat 

 of hair which is getting dry, and another under it which is 

 growing. The hair, which in the quadruped becomes hard 

 and dry to the feel and dingy in the colour, does so prepara- 

 tory to a total though gradual falling off during the summer, 

 sooner or later, in which the whole of the old pile is removed, 



