46 FIELD ORNITHOLOGY. 
‘“ small of the back,” bound closely to the spineg@@sting 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 dull opaque whitish tint. They always 
lie close together. A remarkable fact connected with them is, that they are not always of the 
same size in the same bird, being subject to periodical enlargement during the breeding season, 
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 this 
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 one case the sperm-duet, 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, snipping 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 we 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 or livid bluish, or reddish. There is occasionally but one. The sex 
determined, use the sign g 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; but 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 ornithological 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 one season. These are, in the first place, a peculiar soft fluffy ‘‘ feel” of the 
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, ete., 
of the legs are not sharply cut. Thirdly, the flesh itself is tender and pale colored. These are 
some of the points common 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 the 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 studying, 
for example, the shape of a wing or tail, there is always reason to suspect that the natural 
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