1926]

Swarth: Birds and Mammals from the Atlin Region 77

newly hatched bird grows a set of small-sized wing feathers to accord
with the tiny wing, and these are molted and replaced with others of
the same juvenal type but of larger size. This can be demonstrated
by measurement of corresponding feathers upon the wings of young
birds of different ages.

Fig. C. Tails of Dendragapus obscurus richardsonii, showing variation due to
age; % natural size. a, immature male, during first year (M.V.Z. no. 42642);
b, adult male, in second year or older (M.V.Z. no. 533).

First winter plumage (male): The sexes are unlike at this stage,
nearly as much so as in the fully mature birds. The post-juvenal molt
begins late in July or early in August, inaugurated by the shedding