. Characters of age, sex and sexual maturity in Canada geese. Canada goose; Birds. Fin. ~. — Adult female Canada geese in winter \\ it of former incubation patches. A. piiiinented and, B, unpinmented contour feathers on s^tes ance and a more even coloration. in tlieir second winter of life, and older , lia\e wider— and somewhat stiffer—breast feathers. Although dif- ferences in shape, coloration, and texture of breast feathers might possibly pro\'e useful in aging geese if no other characters were available, the time re- (juired for accurate age determination from these
. Characters of age, sex and sexual maturity in Canada geese. Canada goose; Birds. Fin. ~. — Adult female Canada geese in winter \\ it of former incubation patches. A. piiiinented and, B, unpinmented contour feathers on s^tes ance and a more even coloration. in tlieir second winter of life, and older , lia\e wider— and somewhat stiffer—breast feathers. Although dif- ferences in shape, coloration, and texture of breast feathers might possibly pro\'e useful in aging geese if no other characters were available, the time re- (juired for accurate age determination from these feathers does not make their use an efficient techni(|u('. In late spring and the early part of summer, a sexually mature female that has produced eggs can be distinguished from a sexually immature yearling and from a nonprodiictixe, older adult female by the presence, on the lower breast and belly, of a bare or partially bare area known as an incubation patch, Fig. 6. Tliis area, from which the female has pulled feath- ers during tiie incubation period, is subsecjuently re- feathered. By the onset of the wing molt, or short 1\ thereafter, when the incubation patch has become refeathered, the fresh, unfaded, and unworn feathers stand out in sharp contrast to the worn and faded feathers of the rest of the breast and belly. The patch feathers, therefore, ser\'e to identify a productive fe- male throughout the flightless period in summer. .After this period, the remaining old featliers of the underparts of the body are replaced by new feathers, and the feathers of the patch area may become in- distinguishable from the rest of the underparts. In a small percentage of females, the patch area produces some white or atypically colored feathers. Fig. 7. These feathers are retained until the next spring and hence, during the winter period, indicate the site of the pre- \ioiis incubation patch ( 1959:145). THE WING SPUR The extensor portion of the carpometacarpus bone of the
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