English:
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
View Book Page: Book Viewer
About This Book: Catalog Entry
View All Images: All Images From Book
Click here to view book online to see this illustration in context in a browseable online version of this book.
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
Note About Images
Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work.