File:Characters of age, sex and sexual maturity in Canada geese (1962) (20581291952).jpg

Title: Characters of age, sex and sexual maturity in Canada geese
Identifier: charactersofages49hans (find matches)
Year: 1962 (1960s)
Authors: Hanson, Harold C. (Harold Carsten), 1917-
Subjects: Canada goose; Birds
Publisher: Urbana
Contributing Library: University of Illinois Urbana-Champaign
Digitizing Sponsor: University of Illinois Urbana-Champaign

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Fin. ~. — Adult female Canada geese in winter \\ it of former incubation patches. A. parti.ilK piiiinented and, B, unpinmented contour feathers on s^tes ance and a more even coloration. Gee.se in tlieir second winter of life, and older gee.se, 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 (Han.son 1959:145). THE WING SPUR The extensor portion of the carpometacarpus bone of the wing can be used in aging geese. In the im- matures and yearlings of both sexes in the wintering populations, the skin at this portion of the wing re- mains feathered, Fig. 8A. In adult females, the tip may be partially bare as a consequence of earlier nesting acti\ities. In sexually mature adult males, the tip of the exten.sor portion of the carpometacarpus is en- larged and sometimes notabl\- knobln , and the skin over it is usualh- partialK* denuded of feathers, Fig. 8B. This condition is a behavioral or anatomical artifact, the result of repeated injury in fights with other adult males. The development of a clublike tip to the ex- tensor serves to increase the effectiveness of the wing as a weapon nt defense.

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