File:Characters of age, sex and sexual maturity in Canada geese (1962) (20403586489).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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area of the muscle is particularly larc^e and flat in cross section, Fig. lOB and D, and the extent to which it can be readily e\'erted usually distinguishes females of this age class from yearling females. Fig. lOA and C. The Bursa of Fabricius.—Use of the bursa of Fabricius to distinguish immature from older water- fowl has been described, with reference to ducks, by Gower (1939:427) and by Hochbaum (1942:304-306) and. to Canada geese, by Elder (1946:106-108). Be- cause Canada geese require a longer period to become se.xually mature than do most common species of ducks, the bursa of Fabricius is a useful age criterion for distinguishing yearling geese, in winter, from se.xually mature adults (Hanson 1949:179-180). The depth of the bursa in immatures ranges be- tween 24 and 35 mm. The ax'erage is about 27 mm. In yearlings, it varies between 15 and 24 mm and a\'erages about 20 mm. The bursa is either closed or has been resorbed in approximately 58 percent of geese in their third winter of life; the remainder have a bursal depth varying from 17-21 mm and an a\'er- age depth of 15 mm. Penis characters must be es- pecially carefully evaluated in aging these males. As a criterion of age in Canada geese, the bursa is of value chiefly in separating yearling from older geese, but it must be used in combination with otlier cloacal char- acters. Absence of the bursa can be considered quite certain evidence that a goose is 2"2 or more years of age. Closure of the bursa) opening into the proctodeum of the cloaca apparently proceeds most rapidly during the second year of life, that is, in the age group achiev- ing sexual maturity in the third spring of life. A fe- male, Fig. 6A, shot along the Sutton Ri\'er, Ontario, near the coast of Hudson Bay in early June and judged to be nesting for the first time, had a clutch of three eggs, a \'ery resti"icted incubation patch, and a bursa that had membranous walls that could be probed only with difficulty. She was judged to be nearly 2 years of age. The Oviduct.—In female Canada geese, the mem- Ijrane that occludes the opening of the oviduct into the cloaca is usually not resorbed until after the geese
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Fin.. 11. — Penis of, A. an ijiiiiiatiirc CaiiiKlii nocisc (liiiiiiu the liist winter of lite; li. a \eailiiiH during its sieoiiil winter of life; and, C, an older adult in winter. The sta^e of de\<lopni(nt the peni.s a yearling. O. attains dnrinn its seeond spriii)! of life (an immature tlie ;)re\ ions winter) is nearly eomparahle to that .iKained hy an adnlt. /', in spring. 11

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