WATER FOWL OF INDIA AND ASIA. 37 
pur, Northern Guzerat, Rajputana, the North-West 
Provinces, and Oudh, and near Calcutta. In Sind it 
affects rush-covered swamps, where it occurs in large 
numbers, the birds rising two or three at a time when 
disturbed, not all at once like most Ducks. It is said 
both to whistle and to quack: probably the voices of 
the sexes are different, as is so usually the case. It 
is probable, but not absolutely certain, that it breeds 
in Sind. The eggs are yellowish white, about ten in 
number, and the nest is placed on the ground among 
rushes in the countries where the bird breeds. 
Although differing so little from the female in outward 
appearance, the male of this species yet possesses the 
bony bulb in the windpipe so often found in drakes. 
Inthe other species belonging to thissection, the males 
in undress, females and young have the plumage mot- 
tled with light and dark in a very characteristic way, 
and some look much alike at first ; but they are much 
easier to discriminate than young Pochards. Two of the 
genera are also, as remarked above, easily known by 
pecuharities of form, and the others may generally be 
distinguished by the colour of the wing-bar, which is. 
different in each species, and common to all members 
thereof as arule. The reason for the existence of this 
natural coat-of-arms is an interesting subject for specu- 
lation. 
A theory has been advaneed to the effect that the 
differing markings on the wings of allied birds are “ re- 
cognition marks ”’ whereby the individuals of each spe- 
cies are enabled to know their own kind, and henee verify 
the proverb about birds of a feather flocking together. 
There may be something in this, as it is obviously 1m- 
portant that all the birds in a flock should keep “‘ time ”’ 
and observe formation in their evolutions, and so the 
occasional occurrence of alien individuals in flocks of 
other species cannot be held to be a serious objection 
to the theory. Nevertheless, the Ducks, which furnish 
