CEYLON WATER BIRDS. Sal 
moult into a bright nuptial dress, which they drop by a second 
moult as soon as breeding is over, assuming for the rest of the 
year a plumage similar, or almost similar, to that of the female. 
The drakes, with few exceptions, also differ from the ducks in 
possessing a bony bulb or drum at the base of the windpipe. In 
most forms the exposed portions of the secondary wing 
quills, together with their coverts, are brilliantly coloured, and, 
especially when the wing is closed, form a ribbon-like mark 
known as the wing bar, or “speculum.” This is often more 
conspicuous in adult males than in females and young birds. 
The twelve species on the Ceylon list are divided among 
eleven genera, and fall into three groups :— 
(1) The Walking and Tree Ducks. These resemble Geese 
more nearly than do the other Ducks, and the tarsus is approxi- 
mately equal in length to the bill. Five species, including 
our few common residents, occur in Ceylon. In only one 
case—the little Cotton Teal—does the drake assume a breed- 
ing plumage differing markedly from that of the duck. 
(2) The Surface-feeding Ducks, which are mainly migra- 
tory. In these the tarsus is noticeably shorter than the bill. 
The drakes of all the six Ceylon species possess a brightly 
coloured wing bar, and, with the exception of the Spotted-billed 
Duck, in which both sexes are alike, assume a distinct breeding 
plumage. In the females of several species the wing bar is 
duller or wanting. 
(3) The Diving Ducks ; limited in Ceylon to a single species 
of rather doubtful occurrence. These may be distinguished 
from all other members of the sub-family by the large foot, in 
which the outer toe is as long or longer than the middle toe, 
while the hind toe has a deep lobe. 
Rough Key to Ceylon Species. 
I.—Perching Ducks.—Outer toe shorter than middle toe ; 
bill approximately same length as tarsus. 
A.—Size large ; wing 11 inches or more. 
(a) Lower parts white. 
Sarcidiornis melanonotus (Comb Duck). 
(6) Lower parts reddish-brown. 
Casarca rutila (Brahminy Duck). 
