46 FIELD ORNITHOLOGY. 



" small of the back," bound closely to the spine, resting on the front of the kidneys near their 

 fore end. The testicles are a pair of subspherical or rather ellipsoidal bodies, usually of the 

 same size, shape, and color, and are commonly of a duU opaque whitish tint. They always 

 lie close together. A remarkable fact connected with them is, that they are not always nf the 

 same size in the same biril, being subject to periodical enlargement during the breeding seas(3n, 

 and corresponding atrophy at other seasons. Thus the testicles of a house sparrow, no bigger 

 than a pin's head in winter, swell to the size of peas in April. The ovary (for although thi.s 

 organ is paired originally, only one is usually functionally developed in birds) will be recog- 

 nized as a flattish mass of irregular contour, and usually whitish color; when inactive, it 

 simply appears of finely granular structure which may require a hand lens to be made out ; 

 when producing eggs, its appearance is unmistakable. Both testis and ovary may further be 

 recognized by a thread leading to the end of the lower bowel, — in (jne case the sperm-duct, in 

 the other the oviduct; the latter is usually much the more conspicuous, as it at times transmits 

 the perfect egg. There is no difficulty in reaching the site of these organs. Lay the bird on 

 the left side, its belly toward you: cut with the scissors through the belly- walls diagonally 

 from anus to the root of the last rib, or further, snipjjing across a few of the lower ribs, if these 

 continue far down, as they do in a loon for instance. Press the whole mass of intestines aside 

 collectively, and you at once see to the small of the back. There you observe the kidneys, — 

 large, lobular, dark reddish masses moulded into the concavity of the sacrum (or back middle 

 bone of the pelvis); and on their surface, towards their fore end, lie testes or ovary, as just 

 described. The only precaution required is, not to mistake for testicles a pair of small bodies 

 capping the kidneys. These are the adrenals or " supra- renal capsules," — organs whose 

 function is unknown, but with which at any rate M'e have nothing to do in this connection. 

 They occur in both sexes, and if the testicles are not immediately seen, or the ovary not at 

 once recognized, they might easily be mistaken for testicles. Observe, that instead of lying 

 in front, they cap the kidneys ; that they are usually yellowish instead of opaque whitish ; and 

 that they have not the firm, smooth, regular sphericity of the testicles. The testes, however, 

 vary more in shape and color than might be expected, being sometimes rather oblong or linear, 

 and sometimes grayish cjr livid bluish, or reddish. There is occasionally but one. The sex 

 determined, use the sign $ or 9 to designate it, as already explained. In the very rare cases 

 of impotence or sterility among birds, of course no organs will be observed; bnt I should dislike 

 to become responsible for such labelling without very careful examination. The organs of a 

 small bird out of the breeding season are never conspicuous, but may always be found on close 

 scrutiny, unless the parts are disintegrated by a shot. 



Recognition of Age is a. matter of (.jrnithologieal experience requiring in many or most 

 cases great familiarity with birds for its even approximate accomplishment. There are, how- 

 ever, some unmistakable signs of immaturity, even after a bird has become full-feathered, that 

 persist for at least (jue season. These are, in the first place, a peculiar soft fluffy " fe(d" of tlie 

 plumage ; the feathers lack a certain smoothness, density, and stiffening which they subse- 

 quently acquire. Secondly, the bill and feet are softer than those of the adults ; the corners of 

 the mouth are puffy and flabby, the edges and point of the bill are dull, and the scales, etc., 

 of the legs are not sharply cut. Thirdly, the flesh itself is tender and pale colored. These are 

 some of the points cc.immon to all birds, and are independent of the special markings that 

 belong to the youth of particular species. Some birds are actually larger for a while after 

 leaving the nest, than in after years when the frame seems to shrink somewhat in acquiring 

 . the compactness of senility. On thf! other hand, the various members, especially the bill and 

 feet, are proportionally smaller at first. Newly growing quills are usually recognized on sight, 

 the barrel being dark colored and full of liquid, while the vanes are incomplete. In studyius>-, 

 for example, the .shape of a wing or tail, there is ahi-ays reason to suspect that the natural 



