Text Appearing Before Image: have left their wintering grounds in their third spring of hfe. Therefore, determining the presence or absence of an occUiding membrane at the juncture of the ovi- duct with the cloaca is the best way, in winter, to distinguish females approximately V2 years old from older females. Accurate age determination is of singu- lar importance if the success of the past breeding sea- son is to be estimated from age and sex ratios obtained from trapped biids prior to the hunting season. Studies conducted in preparation for an earUcr report (Han- son 1949:181-182), based on banded birds of known age, indicated there was a high degree of accuracy in differentiating females V2 years of age from those older. In approximately 97 percent of the cases, a female goose that, in fall or winter, has adult-type tail feathers, adult-type primary feathers, and a closed oviduct is approximately P2 years old; if she has an open o\'iduct, she is about 2V2 years of age or older. (In a few^ indi\iduals, the oviduct may open in the second spring of life.) The Penis.—For most species of geese—and es- pecially for the immatures—determining the presence or absence of a penis is essential to accurate se.xing. Eversion of the penis from the cloaca of a male bird Text Appearing After Image: Fig. 12. — Stages of dcvclopmont of tlic penis of Caii.ula geese as shown hy an experiment in\i)l\ing use of light and hormone; A, adult male, untreated in early Feliruary; li. yearling male. Mareh 2. after receiving 16 hours of light a da> for 18 days; C, captive yearling male, April 11, caged outdoors; D. yearling male that received daily, for 4 days, 16 hours of light and gonadotropic lioriuone; E. stage intermediate hetween D and F; F, \earling male. March 2, after being giv'en 16 hours of light and gonadotropic hormone injections daily for 18 days. 12
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== {{int:filedesc}} == {{subst:chc}} {{information |description={{en|1=<br> '''Title''': Characters of age, sex and sexual maturity in Canada geese<br> '''Identifier''': charactersofages49hans ([https://commons.wikimedia.org/w/index.php?title=Special%3...
