2 British Diving Ducks 
or on lakes or rivers near the sea, whilst some nest on the freshwater rivers and lakes. 
The eggs are generally somewhat shorter and thicker than those of Surface-feeding Ducks, 
and the young show a greater aptitude at diving. The flesh has an oily and rancid taste, 
and the down is useful for many purposes. 
The period at which the Diving Ducks become adult varies considerably, some, 
such as the Pochard, being adult and capable of breeding in their first spring, whilst others, 
like the Eiders, take years to acquire their full dress ; but as each species is separately 
treated, and its whole change of plumage from birth to maturity explained in detail, I need 
say no more in this place. The marvellous colour-changes which I first explained and 
described ' in the Surface-feeding Ducks, as being found in that group of birds, are only 
slightly to be seen in the Diving Ducks, and none of them when changing their feathers 
show anything like the sympathetic changes which undoubtedly take place in the case 
of the Mallard and the Wigeon. 
This is not perhaps the place to introduce controversial matter, but I have been severely 
criticised by my friends of the British Ornithologists' Union (the majority of whom have 
never taken the trouble to obtain a large series of Mallard and Wigeon in life and imme- 
diately after death and examine them carefully), who do not accept my views that a feather 
once developed can change colour or alter its pattern. They adhere to the old theory that 
once complete a feather is so much "dead" structure, and can only change by abrasion at 
the tip and by fading. The fact remains, however, that feathers, especially in the case of 
the two above-mentioned Ducks, when passing from spring to eclipse and eclipse into 
winter dress, do change colour as well as fade, and I have exhibited and figured feathers 
that are beyond question what I have asserted them to be — (i) Old feathers of one colour 
and of the old spring dress changing in the last few days of their attachment to the 
bird to a totally different colour and pattern in sympathy and alike to the feathers of 
the incoming plumage of the eclipse ; and (2) new feathers of the winter plumage coming 
in fresh with markings of the old eclipse plumage which soon disappear and become as 
full winter feathers ; (3) feathers of the eclipse plumage itself altering, both by fading and 
colour change, in sympathy with the old spring plumage that is past and with the new 
winter plumage that is to come. 
In cases of old feathers changing colour, such as the bronze-purple ones on a Mallard's 
head, which often change to black spot with light edges, it may be argued that these colours 
are underlying the old and brilliant colours of spring, and to a great extent this is the case, 
but such a contention cannot be advanced in the case of certain feathers on the scapulars of 
the Wigeon, which are new and come in half winter, grey and vermiculated, and half 
eclipse, rich black and chestnut. These feathers are not again moulted, but change to all 
grey with vermiculations in a few weeks by colour change. 
My friend Mr. P. W. Pycraft, who, as a careful biologist, has given particular attention 
to the structure of feathers, has approached this difficult subject with unbiassed mind, and 
the result of his investigations points to the fact that after the feather is once developed 
it cannot change colour or alter its pattern, because there is no visible means of colour 
transmission. Microscopic examination on his part has failed to show that there are any 
channels by which colour or life" can be passed up the quill and the Rami, and from this 
1 The Natural History of the British Surface-feeding Ducks. f '^Ol 
