76 University of California Publications in Zoology [Vou. 30

The distinguishing feature between the two is color. The adult
male of richardsonii is grayish in general appearance with some light
brown mottling on back and sides. In flemingi the brown markings
‘are much reduced and of a darker shade; in general appearance the
fully adult male bird is almost black. In the adult female and in
immatures (natal down and juvenal plumage of richardsonti not
seen), corresponding differences exist. In most cases the distine-
tions between the two subspecies are evident upon the most cursory
examination, and with the exception of one specimen they are uni-
formly maintained throughout the series at hand. The exception is
an immature female of flemingi (no. 44665, head of Surprise Lake,
Atlin region, September 14, 1924), which is much paler than others
from the same general region, and hardly to be distinguished from a
selected specimen of richardson from southern British Columbia.
This bird may be taken to exemplify intergradation by individual
variation between the two subspecies.

The sequence of plumage-changes with age in the grouse of the
genus Dendragapus is sufficiently complicated to be difficult to follow,
and extensive series of specimens are needed to trace the different
stages. An understanding of the development of the individual bird
is, however, absolutely necessary in order to avoid mistakes in making
comparisons between the several forms included in this group.

Taking the subspecies flemingi as a basis, the following stages may
be described as indicating the course of development followed in these
grouse. Dates given apply to conditions in northern British Columbia.

Natal down: Sexes alike. There is no specimen of flemingi at hand
entirely in the down, but comparing small young, still down-clothed
on head and breast, with specimens of sitkensis and fuliginosus at the
same stage, young flemingi is seen to be much less yellow, more gray,
than are the young of those forms.

Juvenal: Again much more gray than in sitkensis and fuliginosus.
Rectrices and remiges begin to appear a few days after hatching, and
the young birds are able to fly long before the natal down is all lost.
The head and neck are the last parts to be clothed in feathers, as shown
in a specimen collected July 8. There is continuous replacement of
plumage on the wings from the time the bird is hatched until it has
finally completed the post-juvenal molt and is practically full grown.
As shown by specimens of young flemingi and of other subspecies also,
there are two complete sets of primaries, secondaries, tertials, and
greater coverts, at least, acquired during the juvenal stage. The