BRANCH CHORDATA (Continued). CLASS AVES: THE BIRDS

THE ENGLISH SPARROW (Passer domesticus)

Technical Note.—The English sparrow may be found now in cities and villages all over the United States. It has become a veritable pest, and the killing of the few needed for the laboratory may be looked on as desirable rather than deplorable, as is the killing of birds in almost all other cases. The males have a black throat, with the other head-markings strong and contrasting (black, brown, and white), while the females have a uniform grayish and brownish coloration on the head.

Specimens are best taken alive, as shooting usually injures them for dissection. One can rely on the ingenuity of the boys of the class to procure a sufficient number of specimens. Observations on the habits of the birds should be made by the pupils as they go to and from school. For dissection use fresh specimens if possible. If desirable a pigeon or dove may be used in place of the sparrow.

External structure.—Note in the sparrow the same general arrangement of body parts as in the toad, the body being divided into head, upper limbs, trunk, and lower limbs. In the toad, however, all of the limbs are fitted for walking and jumping, whereas in the sparrow the anterior pair of appendages, the wings, are modified to be organs of flight, and the posterior limbs are specially adapted for perching. Note that the sparrow is covered with feathers, some long, some short, in some places thick and in others thin, but all fitting together to form a complete covering for the body. Note also that the anterior end of the head is prolonged into a hard bony structure, the bill, covered with horny substance. This horny substance together with the feathers and horny covering of the feet are modified portions of the skin. Note the long quill-feathers attached to the posterior edge of the wing. By these the bird sustains its flight. Other long quill-feathers are attached to the posterior end of the body, forming the tail. By a system of muscles connected with these feathers they act together, serving as a rudder during flight and as a balancing contrivance when perching. Note just above the bill two openings protected by tufts of feathers. What are these openings? How are they connected with the mouth? Note the large eyes, and at the inner angle of each the delicate nictitating membrane which can be drawn over the ball. Does the bird have external ears? Lift the feathers just above the tail (the upper tail-coverts) and note a small median gland, the oil-gland, from which the bird derives the oil with which it oils its feathers. Beneath the tail note the opening from the alimentary canal and from the kidneys and reproductive organs. This is called the cloacal opening.

Examine in detail some of the feathers. In one of the quill-feathers note the central stem or shaft composed of two parts, a basal hollow quill, which bears no web and by which the feather is inserted in the skin, and a longer, terminal, four-sided portion, the rachis, which bears on either side a web or vane. Each vane is composed of many narrow linear plates, the barbs, from which rise (like miniature vanes) many barbules. Each barbule bears many fine barbicels and hamuli or hooklets. The barbs of the feather are interlocked. How is this effected? The feathers which overlie the whole body and bear the color pattern are called contour-feathers. How do they differ from or correspond with the quill-feathers in structure? Soft feathers called down-feathers or plumules, cover the body more or less completely, being, however, mostly hidden by the contour-feathers; the barbs of these are sometimes not borne on a rachis, but arise as a tuft from the end of the quill. Certain other feathers which have an extremely slender stem and usually no vane, except a small terminal tuft of barbs, are called thread-feathers, or filoplumules. They are rather long, but are mostly hidden by the contour-feathers. In certain birds they stand out conspicuously, as the vibrissæ about the nostrils.

In the determination of birds by the use of a classificatory "key" (see p. [359]) it is necessary to be familiar with the names applied to the various external regions of the body and plumage, and with the terms used to denote the special varying conditions of these parts. By reference to figure [133] the names of the regions or parts most commonly referred to may be learned. A full account of all of the external characters with definitions of the various terms used in referring to them may be found in Coues's "Key to North American Birds."

Fig. 133.—Diagrammatic outline of bird's body with names of external parts and regions.

Technical Note.—Pull the feathers from the body, being careful not to tear the skin.