File:Characters of age, sex and sexual maturity in Canada geese (1962) (20402284018).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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crs. Tliis difference is not surprising, as B. c. maxima breeding on Dog Lake, Manitol)a, build nests (KIop- man 1958:169) at least a month earlier tban B. c. in- terior, which nest in the Hudson liay lowlands of northern Ontario and Manitoba. It is advisable to consider both the nesting phenology and the char- acteristics of the indi\'iduals of populations before using collections of tail feathers to obtain age ratios. Primary Feathers. —When some of the immature geese in a population have a complete set of adult- type tail feathers in winter, the outermost primary feathers of the wings fortunately provide the investi- gator with a reliable guide to age determination. The primaries of the immature are pointed; those of the adult are obtuse or rounded, Fig. 3. Cloacal characters in wintering birds provide a nearly infallible guide for distinguishing immature males from adult males; however, the cloacal difference lietween immature and yearling females is largely limited to the depth of the bursa, which is x'ariable. The use of the primary feathers of the wing for age determination probably has its greatest potential value in taxonomic studies of musciun skins. In mak- ing a recent study, in xarious museums, of the skins of races of Canada geese, the author noted specimens that were labeled as to sex but not age or that were incorrectly aged. In these instances a preliininar\- age determination was made by inspection of the tail feathers and, if these were of the adult type, a con- clusi\'e determination was made by inspection of the tips of the primary feathers. Primaries of geese col- lected in late spring or early summer prior to the molt are usually badly faded by the sun, particularly those of immatures. Being pointed and badly faded, the tips of the primary feathers of the immatures stand out in sharp contrast to the fresh, black tail feathers. Fig. 4, which usually are not attained in full complement until at least midwinter, several months after tail feathers of adults have completed growth. Breast and Belly Feathers.—Taverner (19.31 :.31) and Elder (1946:101) have pointed out that breast and belly, or contour, feathers can ser\'e to differenti- ate immatures from older geese. Breast feathers in the ju\enile and postjuvenile plumages of immatures are narrower than in subsequent plumages. They are readily recognized by the prominence of the shaft in each feather, which gives the breast a streaked ap- pearance. Fig. 5. Usually these feathers are replaced during the first winter of life by broader contour feath- ers, which gi\e the underparts a smoother appear-
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FiH. 6. — Iticuhation patches of adult fi-inalo Canada jioe.se during early stage,s of incubation: A, a 2-\car-i>l<l with a clutch of three eggs, June 3; B. an old aihilt with a clutch of seven eggs. May 28.

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