ers. This difference is not surprising, as B. c. maxima 
breeding on Dog Lake, Manitoba, build nests (Klop- 
man 1958:169) at least a month earlier than B. c. in- 
terior, which nest in the Hudson Bay lowlands of 
northern Ontario and Manitoba. It is advisable to 
consider both the nesting phenology and the char- 
acteristics of the individuals of populations before 
using collections of tail feathers to obtain age ratios. 
Primary Feathers. —When some of the immature 
geese in a population have a complete set of adult- 
type tail feathers in winter, the outermost primary 
feathers of the wings fortunately provide the investi- 
gator with a reliable guide to age determination. The 
primaries of the immature are pointed; those of the 
adult are obtuse or rounded, Fig. 3. Cloacal characters 
in wintering birds provide a nearly infallible guide 
for distinguishing immature males from adult males; 
however, the cloacal difference between immature 
and yearling females is largely limited to the depth 
of the bursa, which is variable. 
The use of the primary feathers of the wing for 
age determination probably has its greatest potential 
value in taxonomic studies of museum skins. In mak- 
ing a recent study, in various museums, of the skins 
of races of Canada geese, the author noted specimens 
that were labeled as to sex but not age or that were 
incorrectly aged. In these instances a preliminary age 
determination was made by inspection of the tail 
feathers and, if these were of the adult type, a con- 
clusive determination was made by inspection of the 
tips of the primary feathers. Primaries of geese col- 
lected in late spring or early summer prior to the 
molt are usually badly faded by the sun, particularly 
those of immatures. Being pointed and badly faded, 
the tips of the primary feathers of the immatures 
stand out in sharp contrast to the fresh, black tail 
feathers, Fig. 4, which usually are not attained in full 
complement until at least midwinter, several months 
after tail feathers of adults have completed growth. 
Breast and Belly Feathers—Taverner (1931:31) 
and Elder (1946:101) have pointed out that breast 
and belly, or contour, feathers can serve to differenti- 
ate immatures from older geese. Breast feathers in the 
juvenile and postjuvenile plumages of immatures are 
narrower than in subsequent plumages. They are 
readily recognized by the prominence of the shaft in 
each feather, which gives the breast a streaked ap- 
pearance, Fig. 5. Usually these feathers are replaced 
during the first winter of life by broader contour feath- 
ers, which give the underparts a smoother appear- 
Fig. 6.— Incubation patches of adult female Canada geese during early stages of incubation: A, a 2-year-old with a clutch 
of three eggs, June 3; B, an old adult with a clutch of seven eggs, May 28. 
6 
