THE DUCK.
This bird is of the order of natatores, or swimmers; family, anatidæ, of the duck kind; genus, anas, or duck. The most striking character of the swimming bird is derived from the structure of the feet, which are always palmate—that is, furnished with webs between the toes. There are always three toes directed forward, and these are usually united by a membrane to their extremities; but, in some cases, the membrane is deeply cleft, and the toes are occasionally quite free, and furnished with a distinct web on each side. The fourth toe is generally but little developed, and often entirely wanting; when present, it is usually directed backward, and the membrane is sometimes continued to it along the side of the feet. These webbed feet are the principal agents by which the birds propel themselves through the water, upon the surface of which most of them pass a great portion of their time. The feet are generally placed very far back, a position which is exceedingly favorable to their action in swimming, but which renders their progression on the land somewhat awkward.
THE EIDER DUCK.
The body is generally stout and heavy, and covered with a very thick, close, downy plumage, which the bird keeps constantly anointed with the greasy secretions of the caudal gland, so that it is completely water-proof. The wings exhibit a great variety in their development; in some species being merely rudimentary, destitute of quills, and covered with a scaly skin—in others, being of vast size and power, and the birds passing a great part of their lives in the air. The form of the bill is also very remarkable; in some, broad and flat; in others, deep and compressed; and in others, long and slender.
Most of these birds live in societies, which are often exceedingly numerous, inhabiting high northern and southern latitudes.
The distinguishing characteristic of the family of the anatidæ is the bill, which is usually of a flattened form, covered with a soft skin, and furnished at the edges with a series of lamellæ, which serve to sift or strain the mud in which they generally seek their food. The feet are furnished with four toes, three of which are directed forward, and united by a web; the fourth is directed backward, usually of small size, and quite free. They are admirable swimmers, and live and move on the water with the utmost security, ease, and grace. Such is their adaptation to this element that the young, immediately after being hatched, will run to it, and fearlessly launch themselves upon its bosom, rowing themselves along with their webbed feet, without a single lesson, and yet as dexterously as the most experienced boatman. They are generally inhabitants of the fresh waters, and for the most part, prefer ponds and shallow lakes, in which they can investigate the bottom with their peculiar bills, without actually diving beneath the surface; yet at some seasons they are found along the borders of the sea. Their food generally consists of worms, mollusca, and aquatic insects, which they separate from the mud by the agency of the lamellæ at the margin of the bill; but most of them also feed upon seeds, fruits, and other vegetable substances.