Subfamily ANATINAE

Subfamily ANATINAE.

In the subfamily Anatinae, as restricted in the present work, are included the surface-feeding ducks with a hind toe furnished with a narrow lobe, the tail-feathers normal and the bill always much depressed.

As a rule the drake in this subfamily assumes by moult a nuptial plumage which is discarded for a brief period for a postnuptial dress. In some Indian ducks it is possible that this dress is not always acquired and further evidence is still required to elucidate this point It may eventually be found that the double moult is always undergone, even when there is no change in the plumage.

Another character found in all the drakes of this subfamily is the development of the bulla ossea, or labyrinth, at the base of the trachea, close to the bifurcation of the bronchi.

This bulba ossea is a bony, or partly bony and partly membraneous, dilatation of the lower tracheal rings and is often lateral, as in the common Wild Duck (fig. 75); sometimes, however, this expansion is medial or in two directions, the different forms being characteristic of different genera. The bulba ossea is not found in the other subfamilies except in the Anserinae.

In the Anatinae the bill is depressed and, especially near the tip, much broader than high; the legs are short, placed far back and more adapted for swimming than walking: a brightly coloured patch, known as the speculum, is often found on the exposed bases of the outer secondaries and their coverts.

The subfamily contains twelve genera as found in India. Hartert reduces these considerably, including Anas, Querquedula, Chaulelasmus, Mareca, Eunetta, Dafila and Marmaronetta under the one genus, Anas. On the other hand, certain other systematists go so far as to split up Anas into even further divisions. Blanford's divisions seem simple and sufficient and I retain them in the present work.

Key to Genera.

A. Lower portion of tarsus in front reticulated……………Dendrocygna, p. 410.
B. Lower portion of tarsus in front scutellated.
a. Speculum always present.
a1. Outer web of inner secondaries chest¬nut.
a2. Coloration pied; chestnut, black and white……………Tadorna, p. 414.
b2. Coloration, except quills, all chest-nut of various shades……………Casarca, p. 416.
b1. Outer webs of inner secondaries not chestnut.
c2. Bill not spatulate.
a3. Outer wing-coverts not grey-blue.
a4. Central tail-feathers moderate in length and not elongated.
a5. Bill broad and about the length of the head……………Anas, p. 418.
b5. Bill not broad and shorter than the head.
a6. Tail-coverts longer than the rectrices ……………Eunetta, p. 424.
b6. Tail-coverts shorter than the rectrices.
a7. Central tail-feathers not acuminate and not pro¬jecting beyond the lateral……………Chaulelasmus, p. 426.
b7. Central feathers acuminnate and extending slightly beyond the lateral.
a8. Bill small and about equal in breadth throughout……………Mareca, p. 428.
b8. Bill moderate and tapering towards the tip……………Nettion, p. 431.
b4. Central tail-feathers lengthened and pointed……………Dafila, p. 437.
b3. Outer wing-coverts blue or blue-grey……………Querquedula, p. 439.
b2. Bill spatulate……………Spatula, p. 442.
b. Speculum wanting ……………Marmaronetta, p. 444.

BookTitle: 
The Fauna Of British India, Including Ceylon And Burma-birds(second Edition)
Reference: 
Baker, EC S (1922–1930) The fauna of British India, including Ceylon and Burma. Second edition. vol.6 1929.
Title in Book: 
Subfamily ANATINAE
Book Author: 
Edward Charles Stuart Baker
Year: 
1929
Page No: 
408
Volume: 
Vol. 6
id: 
5255

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