Bill black, with a tinge of green. Iris bright carmine. Upper part of the head, and a space along the base of the bill dusky; a small transverse band of white on what is called the chin; the rest of the head, and the neck all round, for more than half its length, of a rich brownish-red. A broad belt of brownish-black occupies the lower part of the neck, and the fore part of the body, of which the posterior part is of the same colour, more extended on the back than under the tail. Back and scapulars white or greyish-white, very minutely traversed by undulating black lines; wing-coverts similar but darker. Alular feathers greyish-brown. Primary quills brownish-black, tinged with grey towards the base; the shaft brown. Secondaries ash-grey, whitish, and undulated with dark grey towards the end; five of them also having a narrow stripe of black along their outer margin. Tail brownish-grey, towards the end ash-grey. The lower parts white, the sides and abdomen marked with fine undulating grey lines, of which there are faint traces on most of the other feathers. The feet are greyish-blue tinged with yellow.
Length to end of tail 22 inches, to end of wings 20, to end of claws 25; extent of wings 33; wing, from flexure, 9 3/4; tail 2 10/12; bill along the back, measured from the tip of the frontal process to the end of the unguis, 3; lower mandible along the edge 2 7/12; tarsus 1 3/4; first toe 6/12, its claw 5/12; middle toe 2 10/12, its claw 5/12; outer toe scarcely shorter; inner, 7/12 shorter. Weight 3 3/4 lb.
Adult Female. Plate CCCI. Fig. 2.
The Female has the bill coloured as in the male; the iris reddish-brown; the feet lead-grey; the upper parts greyish-brown; the top of the head darker, its anterior part light reddish; the chin whitish; the neck greyish-brown, as are the sides and abdomen; the breast white; wing-coverts brownish-grey; primary quills greyish-brown, dusky at the end; secondary quills ash-grey, five of the inner with an external black margin, the innermost greyish-brown like the back, and with some of the scapulars faintly undulated with darker. Tail greyish-brown, paler at the end; axillars and smaller under wing-coverts white, as in the male.
Length to end of tail, 20 1/4 inches, to end of wings 18 1/2, to end of claws, 23 1/4; extent of wings, 30 3/4: wing from flexure, 9 1/4. Weigh 2 3/4 lb.
This species is very closely allied to the Pochard, or Red-headed Duck, Fuligula Ferina, but is much larger, and differs in having the bill proportionally higher at the base, and less dilated towards the end. The colours are also generally similar, but present differences. The upper parts of the Canvass-back are much whiter than those of the Pochard; the head of the former is dusky above, of the latter uniform with the neck; and the white spot on the chin is wanting in the Pochard.
The Digestive and Respiratory Organs of a male shot near Baltimore present the following characters.
The upper mandible is broadly and deeply concave. The tongue, which is thick and fleshy, as in other ducks, is 2 2/12 inches long, its sides parallel, slightly sloping, and furnished with two series of bristly filaments; its base with numerous straight conical papillæ directed backwards, its upper surface marked with a broad median groove, the lower flat, its extremity formed by a thin semi-circular appendage, a quarter of an inch in length. The œsophagus passes along the right side of the neck, for six inches has a diameter of 5/12 then dilates to 9/12, so as to form a slight crop, again contracts as it enters the thorax, and in terminating forms the proventriculus, which is 1 3/4 inches in length, with oblong glandules, generally a twelfth of an inch in length. The stomach is a very large and powerful gizzard, of a broadly elliptical form, with extremely thick lateral muscles, the left being 11/12 in thickness, the right 10/12, the tendons large and strong. The transverse diameter of the gizzard is 2 11/12 inches, the longitudinal, from the cardiac orifice to the bulge of the inferior muscle, 2 1/12. Its cuticular lining is of very dense texture, and rugous; the grinding plates opposite the lateral muscles about half a twelfth thick, and slightly rugous. The intestine, which is 5 feet 9 inches in length, first forms in the usual manner the duodenal fold, at the distance of 5 inches from the pylorus, encloses the pancreas, receives the biliary ducts, and passing under the right lobe of the liver, proceeds backward beneath the kidneys, is convoluted in several large folds, and finally from above the stomach, passes in a direct course to the anus. Its coats are thick, its inner surface villous, and its diameter is considerable, being in the first part of the duodenum 9/12, then for two feet from 5/12 to 4/12, enlarged again to 6/12, and so continuing to the rectum, which is 6 inches long, 1/2 inch in diameter, and ends in an enlargement or cloaca, about an inch in diameter. The cœca, which commence at the distance of 6 inches from the anus, are 8 inches long, slender, 2/12 in diameter for 3 inches, afterwards about 3/12, with the extremity obtuse. The œsophagus and stomach contained young shoots of Zostera marina, and in the latter were numerous particles of quartz.
The trachea, when moderately extended, measures 10 inches in length, and is furnished with strong lateral or contractor muscles, a pair of cleido-tracheal, and a pair of more slender sterno-tracheal. Its diameter at the upper part is 4 1/2 twelfths, it gradually contracts to 3 1/2 twelfths, enlarges to 4 1/2 twelfths, and at the distance of 7 1/4 inches from the upper extremity, forms a dilatation about an inch in length, and 7/12 in its greatest diameter, but composed of distinct rings, then contracts to 5/12, and ends in a bony and membranous expansion, forming on the left side an irregular thin disk, convex towards the right, and flattened towards the left where it is membranous. The expansions of the trachea are thus similar to those of the Red-breasted Merganser, but of less extent; the rings are of equal breadth on both sides, but alternately overlap each other, one side being partially concealed by the corresponding sides of those above and below it, while the other stands exposed. The lower larynx is formed of ten united rings, together with the bony and membranous expansion described. The tracheal rings, rather broad and osseous, are 118; the half-rings of the bronchi about 16.