84 THE ZOOLOGIST. 
this occurs in Perdix cinerea,* Tetrao bonasia (in which 
the summer feathers are generally like down on the 
points of the new growing autumn feathers), tetrix and 
urogalloides. t 
IV. Triple Moult, or a conjunction of the spring, summer 
and autumn moults. 
A. Entire; including almost all the small feathers, as in 
Lagopus alpina and subalpina; although during the 
summer an almost continuous moult takes place with 
these birds, three distinct plumages may still be plainly 
observed, viz. the darker spring, the lighter summer (or, 
more properly, the autumn dress, as it is not donned 
until September), and the white winter dress. 
B. Partial, embraces the small feathers of the head, neck and 
under parts. The nuptial dress begins to show itself 
towards the spring, and is complete about the end of 
April, and is cast again about the beginning of July. 
This occurs with Podiceps auritus, Linn. (Podiceps cor- 
nutus, auct.), which becomes, in its summer plumage, 
Podiceps arcticus, auct., and also with Graculus carbo and 
cristatus. The former of the two last-named has, in 
November, on its head quite short blackish-blue feathers, 
and on its neck grey-brown feathers with a slight blue 
tinge. From this dress it passes, by change of feathers 
during the winter, by degrees to the nuptial dress. 
Whether the other Grebes assume a particular summer 
plumage I have not myself had an opportunity of observing, but 
the subject is worthy of careful investigation. 
Besides these changes of plumage caused by the old feathers 
being entirely cast and fresh ones growing, many birds, especially 
such as have only a single moult (but also some that moult 
several times), undergo a very visible change of colour towards 
the spring; namely, by losing certain portions of their feathers, 
which operation is here commonly termed “ brimfillning,” or 
* W. von Wright, ‘Gétheb. K. V. S. Handl. 1850,’ p. 78. 
+ Tetrao wrogalloides, therefore, inherits this from its father, the Blackcock, 
as this summer plumage does not seem to occur so far as the Capercaillie is 
concerned, 
