5. External portion of sphincter muscle, Fig. 10A, not 
much larger than that of immature and light flesh- 
red in color; oviduct closed at juncture with cloaca; 
bursa open and easily probed, usually to a depth of 
15-20 mm, as in yearling male...... yearling female 
External portion of sphincter muscle, Fig. 10B, much 
larger than that of either immature or yearling fe- 
male and dark red or blotched with purple; oviduct 
open and easily probed; bursa closed or, if open, 
shallow and probed only with difficulty. . .adult female 
Gn benisspresents Bugs iA rer pyeeteicesie etek immature male 
Penis Absentistj.,.<i00e steelers lois sate otereusie sre immature female 
On the breeding grounds, in the spring and sum- 
mer, the problems of aging geese are more complex 
and subtle than on the wintering grounds in fall and 
winter. A male possessing an adult-type tail and a 
penis that indicates sexual maturity is, nevertheless, 
only 1 year of age if tips of the primary feathers are 
pointed, worn, and faded. A year-old female, prior 
to the molt in her second summer of life, possesses 
primaries with pointed tips and, with very few ex- 
ceptions, a closed oviduct. A year-old goose of either 
sex still retains a large, easily probed bursa. 
A 2-year-old goose, after its return to the breeding 
grounds for the third summer of life, cannot be iden- 
tified with certainty; in individual cases, however, 
identification based on a combination of characters 
may be accurate. An incompletely resorbed bursa to- 
gether with a normal uninjured wing spur indicates 
a 2-year-old male; an older male Jacks a bursa and, 
in all probability, has a knobby, enlarged wing spur. 
A female possessing an open oviduct, a remnant of 
a bursa, and either a very small or no brood patch 
may be considered 2 years old. An older female, par- 
ticularly one in the process of egg-laying, has a flaccid, 
easily distended sphincter muscle, an enlarged ovi- 
duct opening, and a prominent brood patch. In a 
female of either age class, the presence or absence of 
a brood patch in midsummer should indicate whether 
or not the individual had attempted nesting in the 
current season. 
The question has often been posed as to what per- 
cent of the 2-year-old females nest in their third spring 
of life. To determine the answer for a large and widely 
scattered population would be difficult and expensive. 
It would be necessary to collect a statistically signifi- 
cant number of females early in the nesting cycle, 
determine the percentage of 2-year-old females (aged 
by bursa examination), and then relate the data ob- 
tained to the percentage of yearlings identified in the 
population the previous winter. At the present time, 
or until more definitive characters of age in breeding 
geese are found, a program that attempted estimates 
of this nature for large and widely scattered popula- 
tions as its chief objective would have dubious merit. 
On the other hand, a program dealing with a non- 
migratory wild population of limited size 
a popula- 
14 
tion that could be aged, banded, and subsequently 
closely observed—would provide information on the 
percentage of females that nest at 2 years of age. 
For example, recent studies of refuge populations 
in the United States indicate that from one-third 
to two-thirds or more of the 2-year-old females may 
breed. Doubtless the percentage that breed in any 
single year is related to the density of older breeding 
pairs present and to the extent that other pairs have 
been broken up due to the death of one of the mem- 
bers. Hence, the statistics obtained from any one 
population would not apply exactly to other popula- 
tions. 
At the present stage of our knowledge, predictions 
dealing with heavily shot populations should probably 
be based on the assumption that all females attempt 
to nest at approximately 2 years of age or in their 
third spring of life. Predictions of fall populations may 
be calculated by using an average figure of produc- 
tivity for all females 2 or more years of age. However, 
the productivity of 2-year-old females is generally re- 
ported to be one bird less than for older females. 
LITERATURE CITED 
Beebe, C. William, and L. S. Crandall 
1914. Specialization of tail down in certain ducks. Zoologi- 
ca. 1(13) :248—252. 
Elder, William H. 
1946. Age and sex criteria and weights of Canada geese. 
Jour. Wildlife Mgt. 10(2):93-111. 
Gower, W. Carl 
1939. The use of the bursa of Fabricius as an indication 
of age in game birds. N. Am. Wildlife Conf. Trans. 
4:426-430. 
Hanson, Harold C. 
1949. Methods of determining age in Canada geese and 
other waterfowl. Jour. Wildlife Mgt. 13(2):177-—183. 
1959. The incubation patch of wild geese; its recognition 
and significance. Arctic 12(3):139-150. 
Hanson, Harold C., and Robert H. Smith 
1950. Canada geese of the Mississippi Flyway with special 
reference to an Illinois flock. Ill. Nat. Hist. Surv. 
Bul. 25(3):67-210. 
Hochbaum, H. Albert 
1942. Sex and age determination of waterfowl by cloacal 
examination. N, Am. Wildlife Conf. Trans. 7:299- 
307. 
Klopman, Robert B. 
1958. The nesting of the Canada goose at Dog Lake, Mani- 
toba. Wilson Bul. 70(2):168-183. 
Schigler, E. Lehn 
1924. Om de skandinaviske A=nder, deres Dragtskifte og 
Traek. Dansk Ornithologisk Forenings Tidsskrift 18: 
85-95. 
Taverner, P. A. 
1931. A study of Branta canadensis (Linnaeus), the 
Canada goose, Can. Natl. Mus. Bul. 67:28—40. 
