is a simple matter in ducks; in geese, because of the 
larger size and greater strength of the sphincter mus- 
cle, eversion is more difficult. The technique is the 
same in both cases—application of a firm downward 
and outward rolling pressure of the thumbs when 
placed on either side of the sphincter muscle. The 
forefingers are used to bend the tail back to aid ever- 
sion of the cloaca. At the same time an upward pres- 
sue is applied from below the bird by a lateral surface 
of the middle finger of each hand. Experience in sexing 
geese and in examining the cloaca with the speculum 
is probably best gained, at first, by working with dead 
birds. 
The presence of an immature penis in a wild 
goose being examined immediately identifies the bird 
as an immature male. (Captive geese sometimes de- 
velop more slowly than wild geese, and some cap- 
tive yearling males may have immature penes.) The 
everted penis of an immature will be seen as a small, 
corkscrew-shaped organ (about the size of the ex- 
posed lead tip of a sharpened pencil) situated in the 
8 o'clock position, Fig. 11A. 
Present in female geese is a small papilla on the 
internal edge of the sphincter muscle. This papilla, 
situated in the 6 o'clock position, is minute in im- 
matures but somewhat larger in older females. It is 
believed to be homologous to the clitoris in mammals. 
The penis of the yearling male goose in winter, 
Fig. 11B, can be described as intermediate in size be- 
tween that of an immature and an adult, Fig. 11A and 
C. In the great majority of instances, penis characters, 
when considered together with the bursa, are useful in 
distinguishing yearling adults from older adults. The 
penis in yearlings is about 4 mm in diameter and 10 
mm long. Its most salient features, a pale, translucent 
color and a smooth surface appearance, Fig. 11B, tend 
to give it a rather turgid aspect. 
The sheathed and unextended penis in older geese, 
in winter, is generally one and one-half to two times 
as large as this organ in typical yearlings. It is usually 
a darker red than the penis in yearlings and is some- 
times tinged with purple, particularly toward the 
distal end. The surface of the sheath is wrinkled in 
appearance, and the visible venation is more prom- 
inent than that of yearlings. 
No discernible change in the development of the 
penis is seen in wintering immatures prior to north- 
ward migration in late February and early March, 
but in yearlings and adults some enlargement and a 
tendency to become unsheathed may be noted. By 
the time Canada geese arrive on the breeding grounds 
in late April and early May, the penes in all age classes 
have undergone notable development, Fig. 11D and 
E, particularly the penis of the immature. In the 2- 
month interval between departure from the winter- 
ing grounds and arrival on the breeding grounds, the 
penis of the immature, Fig. 11D, undergoes develop- 
ment nearly comparable to that of the adult in spring, 
Fig. 11E. However, the immature still possesses a large 
bursa, Fig. 10D, and in most cases immature tail 
feathers, which provide incontestable evidence that 
the bird is, indeed, only a 1-year-old. 
The maturation of the penis can be observed in 
a series of photographs, Fig. 12, taken in the course 
of an experiment on the effects of increased light and 
of daily injections of gonadotropic hormones on the 
maturation process. 
DISCUSSION AND SUMMARY 
In addition to the principal characters of age and 
sex discussed above, there are general clues to the 
age and sex of the bird being handled. For example, 
birds in the various age and sex classes vary con- 
siderably in size. In winter, the weight of an immature 
Branta canadensis interior averages about 1%2 pounds 
less than that of the adult; the weight of a yearling 
averages one-half pound less. Males are heavier than 
females by an average of nine-tenths of a pound in 
the immature and yearling age classes and 142 pounds 
in the adult age class. These differentials in weight 
are reflected in muscular development. With experi- 
ence, an operator should have a fairly accurate idea 
of the age and sex of a live goose simply by grasping 
it by the humeri. The muscles around the humeri of 
immatures are not fully developed and they feel 
stringy; those of older geese, particularly adult males, 
are well developed. The inexperienced can most ef- 
fectively learn to sex and age geese in fall and winter 
by using the key below: 
1. Some or all tail feathers with notched, worn tips and 
relatively narrow vanes, Fig. 2A, B, D; color blackish 
Dic uirieeereyie on car neeaie mieten ict eioue aoe cc’ Siew vais 6 
All tail feathers with unnotched, unworn tips and 
relatively broad vanes, Fig. 2C; color black...... 
2. Primaries pointed at tips, Fig. 3B.............. 6 
Primaries obtuse or rounded at tips, Fig. 34...... 3 
Oo CIS tDLONC Mba aha etaTura iWin Sietsia eis Wisre is «// bis sia alalais.eje 6's 4 
Jape} Che) cs Ak GAs Seon icaee UG nO Caer 5 
4. External portion of sphincter muscle a pale flesh 
color; penis intermediate in size, Fig. 11B, usually a 
pale flesh color, translucent and smooth; bursa open 
and easily probed, usually to a depth of 15-20 mm; 
spur of each wing smooth and feathered over at tip, 
Oy ee ayo a an ie A ee yearling male 
External portion of sphincter muscle dark red or 
purple; penis large, Figs. 11C and 12A, dark red or 
purplish in color, with wrinkled surface and fairly 
prominent venation; bursa closed or, if open, shallow 
and probed with difficulty; tip of each wing spur en- 
larged and knobby at tip and more or less denuded 
OLMLentUPIS OIE OD eee hess trv hateele so oe adult male 
13 
