THE MOULTING OF THE KING PENGUIN. 
119 
ptarmigan moults several times annually, not because its reptilian ancestors frequently 
moulted, but rather that it may in summer and autumn as well as in winter have 
the advantage of being protectively coloured. Probably the changes in the plumage 
of grouse are also adaptive ; but why, in pigeons, new feathers are being substituted 
for old during the greater part of the year is not so obvious. 
It is extremely difficult (even if one adopts the doctrine of sexual selection and 
admits that much is gained by being protectively coloured) to account for the many 
peculiarities met with in the plumage of birds. It would not cause much surprise 
should an ornithologist with a bias in favour of Lamarckism arrive at the conclusion 
that birds have a keen appreciation of both form and colour, and have in fact long 
been striving to acquire as fine a plumage as the circumstances under which they 
live and move and have their being permitted. A Neo-Lamarckian might even 
assert that, notwithstanding the necessity to moult, birds have long been endeavouring 
not only th obtain as brilliant a nuptial plumage as possible, but to wear fine feathers 
all the year round. As a matter of fact, many birds, without incurring undue risks, 
acquire at a very early period, and perpetually wear, fine feathers, while others wear 
a fine coat during a considerable part of each year. The chief difficulty encountered 
was the renewal of the flight feathers without the loss of the power of flight. King- 
fishers and many other birds which early assume the nuptial coat and wear it 
throughout the year have overcome this difficulty by only moulting a few of the 
wing quills at a time — the use of the wings being assured all the year round, there 
was probably little difficulty in reducing or suppressing the nestling down stagehand 
in exchanging the old for new feathers so gradually that the brilliancy of the 
plumage was maintained almost unimpaired all the year round. 
In the case of the Great Northern Diver an ideal plumage has only been partially 
realised, apparently because all the flight feathers are lost at or about the same time. 
Hence, although in both sexes a fine nuptial dress has been acquired, it cannot be 
safely worn when the wings are out of action. If our more familiar birds — e.g. 
thrushes, starlings, and pigeons — were annually to lose for some weeks the use of 
their wings they would run the risk of being rapidly exterminated. In aquatic 
birds the power of flight is not, as a rule, as imperative as in land birds. Neverthe- 
less, in the Great Northern Diver — a bird so highly specialised for an aquatic life 
that walking on land is no longer possible — the loss of the power of flight is probably 
so serious that, in order to diminish the risk when the wings are out of action, the 
brilliant nuptial coat is for a time exchanged for a sober inconspicuous coat. This 
implies that the Great Northern Diver (the female as well as the male) moults twice 
a year. The nuptial plumage gives place at the end of the breeding season to a 
sober post-nuptial or" winter plumage, and this in turn gives place to the brilliant 
nuptial plumage. Though the t wing quills are not shed until about the end of 
December, the moulting of the inconspicuous winter coat begins about the beginning 
of December, but the progress is so slow that the new nuptial coat — characterised 
