1 1 8 British Diving Ducks 
The specimen described accurately by Dresser has been kindly sent to me for examina- 
tion by the Curator of the Birds, Manchester University Museum. It was collected by 
Sabanaeff, being taken on July i8, 1872, at Kimschensk, N. Russia. The whole appearance 
is very like that of the young Golden-Eye in down, but the bill is narrower and longer 
and has a very bright bone-yellow nail. The tail too is very large, like all the juvenile Mergi. 
Immature Male. — The young male in first plumage very closely resembles the adult 
female and young female, and until December it is very difficult to tell the sexes apart 
except by dissection. At the end of five months, however, the young male begins to turn 
much darker. The nape is now often changed to new black feathers and the upper wing 
has a larger area of white ; the lores too show many dark feathers. The tail is often com- 
plete by December. So the advent of the male plumage continues to advance on the upper 
parts until April when the usual halt takes place, until an eclipse plumage, closely resemb- 
ling that of the adult male, is assumed. The wings, which are always the key to identifica- 
tion, are not the same as the adult male, and always have more or less brown or blackish 
edges on the upper coverts instead of being the pure white of the adult male. 
The immature male passes through the same stages as the other Mergansers and 
assumes its first complete plumage in late November— that is, at seventeen months. 
Adtilt Male. — Lores and a large patch round the eye and nuchal patch jet black; the 
rest of the head, neck, and under parts pure white ; generally a faint line of black feathers 
extends from the back of the eye to the back of the head. Crown feathers elongated, 
forming a white crest which in moments of excitement is split in the middle of the crown, 
forming a double crest. Centre of the back and two narrow lines, one across and the other 
touching the scapulars on the sides of the upper breast, black ; scapulars white, the outer 
feathers tipped with black ; lower back black, turning to greyish-brown on the rump ; tail 
greyish-brown ; a little grey across the vent ; flanks white and finely vermiculated with 
black ; primaries blackish-brown ; long inner secondaries grey with white edges, their one 
white feather edged with black and central secondaries black with white; median wing 
coverts white ; lesser wing coverts black ; bill bluish-slate ; nail inclined to bone-colour ; 
irides white; legs and feet lead-blue with darker webs. Length, 164 inches; wing, 7.6 
inches; tarsus, 1.3 inch. 
The adult male assumes its eclipse plumage in June. As Naumann points out, it closely 
resembles that of the adult female, though I fancy that the bird from which his description 
was taken was not yet in full eclipse, as it differs somewhat from those I have seen. 
In July the adult male has gained a very rich red-brown crest, somewhat fuller than 
the female, and it can always be distinguished from the female by the rich colouring of the 
wing, the white irides, and the black patch round the front of the eyes ; also by its larger 
size, black edges to outer white scapulars, and a few vermiculated feathers above the thighs 
on the flanks. In other respects the whole of the rest of the plumage is like the adult 
female, except the mantle, which is nearly black. Wings as in winter. The autumn moult 
proceeds in the usual manner, and the adult male regains its winter plumage by the end of 
November. Sometimes a few eclipse plumage feathers remain in the plumage until the 
new year, but this is unusual.^ 
1 For a description of the eclipse plumage, see also Naumann and J. L. Bonhote, Avicultural Mag., new series, vol. iii. 
(1904-1905), p. 120. 
