218 BRITISH) SEX (BIRDS: 
most remarkable fact that the drake of this species 
assists the duck in bringing up the young, but not, so 
far as I can learn, in incubating the eggs. During 
the whole breeding season this Duck is remark- 
ably tame, loth to take wing, and swimming out 
into the centre of the lake for safety, if threatened 
by danger. The winter migrations of this Duck 
are not very extended, the Mediterranean Basin, 
perhaps, marking the extreme southern limits. 
MERGANSERS. 
The Mergansers are a well-defined little group of 
fish-eating Ducks, forming the sub-family Mergine. 
They are characterised by their slender, narrow bill, 
furnished on both upper and lower mandible with 
saw-like lamellz or denticulations. The head is 
always more or less crested ; in most other respects 
they resemble the Diving Ducks, all the species 
seeking for their food by diving. The sexes differ 
in colour of plumage, but not, perhaps, to such a 
marked extent as in some other divisions of the 
ANATID&. Six species of Mergansers are known to 
science, of which four are included in the British 
list—one as a rare visitor from North America. 
Of the remaining two species, one inhabits South 
America, the other the Auckland Islands. The 
young, as usual, are hatched covered with down, 
and able soon to follow the female to the water 
In their moulting and progress to maturity they 
resemble preceding species. 
