Subfamily ANATINAE

This subfamily, as here defined, contains the typical Ducks together with the Sheldrakes, the Spur-winged " Geese," the Diving Ducks, and the Stiff-tailed Ducks, or the Plectropterinae, Fuligulinae, and Erismaturinae of many ornithologists. The principal character by which these groups are distinguished, the lobation of the hind toe, varies too much in different genera to be used as a criterion for the distinction of larger groups, there being a considerable amount of passage between forms in which the toe is simple, through typical Ducks with a narrow lobe, to the broadly lobed Pochards and Diving Ducks ; whilst neither the spiny tail of Erismatura nor the wing-knob of Plectropterus appears to entitle its owner to more than generic rank.

As a rule, the drake in this subfamily assumes by moult A special nuptial plumage for a longer or shorter period, but the exceptions are numerous, especially amongst resident Indian species. There is, in the forms assuming a nuptial plumage, a double moult of the body-feathers, the two moults sometimes, as in the Common Mallard, occurring at an interval of only three or four months.

Another character found in almost all drakes of this subfamily is the development of a bulba 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 (tig. 104) ; but sometimes the expansion is medial or in two directions, the different forms being characteristic of particular genera. This peculiar conformation is found in the Merginae, but not in the Anserinae.

The bill throughout the subfamily is depressed, and, especially near the tip, much broader than high. The legs are rather short and more adapted for swimming than for walking. In the majority the exposed portions of the secondary quills, with their larger coverts, are distinguished by conspicuous and often metallic Coloration. The brightly coloured patch thus formed is known as the "speculum."

Key to the Genera*

a. Hind toe not lobed or narrowly lobed. Breadth of lobe or web less than one-third length of toe.
a1. Nostril one-third length of bill from fore¬head.
a2. Size large : wing over 10 inches.
a3. Breast and abdomen white ; male with a large fleshy Comb at base of culmen………………….. SARCIDIORNIS, [p. 422.
b3. Breast and abdomen brown tinged with rusty red………………….. ASARCORNIS, p. 424.
c3. Breast and abdomen dark brown, head pink………………….. RHODONESSA, p. 425.
d3. Abdomen black in the middle, white at the sides………………….. TADORNA, p. 427.
e3. Breast and abdomen ruddy ochreous………………….. CASARCA, p. 428.
b2. Size smaller : wing under 10 in.; tarsus reticulated throughout………………….. DENDROCYCNA, [p. 430.
b1. Nostril less than one-third length of bill from forehead.
c2. Size Very small wing under 7 in.; bill high at base and short………………….. NETTOPUS, p. 4.33.
d2. Wing not less than 7 inches.
f3. A speculum present, either metallic or black and white.
a4. Bill not spatulate, and but little if at all broader near the tip.
a5. Upper wing-coverts not blue nor bluish grey.
a6. Tail moderate, median rectrices not lengthened.
a7. Lamellae fine, projecting considerably beyond mandibles; speculum black ana white…………………..CHAULELASMUS, [p. 440.
b7. Lamellae moderate, not projecting ; speculum partly or wholly green or purple. Bill from forehead longer than tarsus.
a8. Tail of 18 or 20 feathers………………….. ANAS, p. 435.
b8. Tail of 14 or 16 feathers.
a9. Nail about one-third width of bill ; head of male crested and tertiaries falcate………………….. EUNETTA, p. 438.
b9. Nail less than one-third width of bill; no crest nor falcate tertiaries………………….. NETTIUM, p. 441.
c9. Nail more than one-third width of bill; no crest nor falcate tertiaries………………….. MARECA, p. 445.
b6. Median rectrices lengthened and pointed………………….. DAFILA, p 447.
b5. Upper wing-coverts lavender-blue………………….. QUERQUEDULA,
b4. Bill spatulate, nearly twice as broad near tip as near base………………….. SPATULA, p. 451. [p. 449.
g3. No speculum; sexes alike; plumage dull greyish brown………………….. MARMARONETTA, [p. 454.
b. Hind toe broadly lobed, breadth of lobe one-third to one-half length of toe.
c1. Tail less than half length of wing.
e2. Upper mandible at base not so high as broad.
h3. Bill viewed from above tapering slightly from base ; tail-feathers 16………………….. NETTA, p. 455.
i3. Bill not tapering ; tail-feathers 14………………….. NYROCA, p. 458.
f2. Upper mandible at base higher than broad………………….. CLANGULA, p. 464.
d1. Tail half as long as wing; bill much swollen at base………………….. ERISMATURA, [p. 465.

* This Key does not always serve for species not found in India,

BookTitle: 
The Fauna Of British India, Including Ceylon And Burma-birds
Reference: 
Blanford, William Thomas, ed. The Fauna of British India: Including Ceylon and Burma. Vol. 4. 1898.
Title in Book: 
Subfamily ANATINAE
Book Author: 
William Thomas Blanford
Year: 
1898
Page No: 
420
Volume: 
Vol. 4
id: 
2309

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