92 University of California Publications in Zoology [Vou.30

In young birds, too, the first ‘‘winter plumage, preliminary”’ is
only partly acquired. Over the whole of the lower parts below the
upper breast the molt is direct from the juvenal to the white winter
plumage. On the head, neck, and dorsum, the ‘‘first winter, pre-
liminary’’ is partly acquired, but white feathers appear on the chin
and throat long before the juvenal plumage is lost on back and flanks.
Young birds of alerandrae at hand (Willett coll.), taken in October,
are in ‘‘first winter, preliminary,’’ almost complete. There are but a
few juvenal feathers left to distinguish young from old. In every case,
though, young birds and adults may be distinguished by the differently
shaped tertials, which linger longer than almost any other feathers of
the brown-colored plumages.

On September 1, adults from the Atlin region had almost all
acquired new flight feathers and rectrices. In the young, the juvenal
rectrices are lost at a very early age, before the bird is half grown,
being almost the first of that plumage to go. On September 1 nearly
all young birds seen had completely acquired the black rectrices of
the first winter plumage, slightly narrower than in adults but not
otherwise different.

To summarize these details of plumage, they all go to show the
incomplete nature of the ‘‘winter plumage, preliminary,’’ inserted
between the breeding plumage and the white winter plumage in adults,
between the juvenal plumage and white winter plumage in young
birds. Judging from material at hand it is less perfectly acquired at
the northern limit of the range of the willow ptarmigan, and more
perfectly acquired toward the southern limit, where longer summers
give more time before the white winter plumage is essential. On the
islands of southeastern Alaska, the habitat of Lagopus l. alexandrae, a
region of relatively mild winters, the ‘‘winter plumage, preliminary’’
is acquired more nearly to perfection than perhaps anywhere else in
the general range of the species. As a result of the perfect acquisition
of this plumage in this particular dark-colored race, we see fall birds
that closely resemble the Scotch red grouse (as described above), which
bird, of course, is a southern species of Lagopus which does not acquire
a white winter plumage at all.

In this account of the plumage variations of the several subspecies
of the willow ptarmigan here under consideration I have used through-
out the terminology employed by Dwight (1900, p. 147) in his exposi-
tion of the seasonal and other changes undergone by these birds. My
own observations (made much easier through a previous reading of