56 University of California Publications in Zoology [Vou 30

Canada jays; the absence of these factors may have been the favorable
feature of the place. The nesting species of gulls and tern were not so
fortunate, for they suffered severely from the raids of herring gulls, to
the ultimate destruction of nearly all the young that were hatched.

OTTER CREEK

The upper portion of Otter Creek (3500 to 4000 feet altitude),
where we worked for two weeks, may be described as characteristic of
vast areas throughout this region that lie in an intermediate position
between the wooded lowlands such as border Lake Atlin and the
timberless mountain tops. Willow is the dominant forest growth
along the bottom of this valley, never as large trees but as densely
growing, rounded bushes, rarely more than twenty feet high and
usually much lower. On Otter Creek, as on some other streams, the
necessities of hydraulic mining have caused the damming of the stream
far up the valley. For miles above the lake thus formed the valley
floor is transformed into a willow swamp, a haven for ducks.

The mountain slopes on either side, and much of the valley floor
in the upper reaches of the stream, are dry and more sparsely covered
with vegetation. There are extensive grassy areas, and at about 3800
feet altitude the creeping birch begins to be conspicuous. Mostly
this is a rather innocuous shrub, low-growing and easily walked over
or avoided, but I found some sections (at about 4000 feet altitude)
where it formed a chaparral on hill sides and ridges ten feet high or
more and well-nigh impenetrable.

On the surrounding mountain sides, especially on north and east
facing slopes, spruce, and above that, balsam, grow in small groves in
some places, in solid stands for miles on favored exposures. On Spruce
Mountain, forming the western boundary of Otter Creek Valley, this
forest ceased abruptly between 4500 and 5000 feet altitude. Above
that boundary grassy slopes and ridges prevail, with a very little false
heather in places and a few scattered thickets of balsam.

ZONAL AND FAUNAL POSITION OF THE ATLIN REGION

Atlin occupies a position relative to the coast about the same as
Telegraph Creek, in the Stikine Valley, and Hazelton, in the Skeena
Valley, 150 miles and 375 miles to the southward, respectively. Both
of these places I had visited in previous years (see Swarth, 1922, 1924),
and comparisons between the regions naturally follow. Atlin Lake is at