GEOGRAPHICAL SURVEYS WEST OF 100TH MERIDIAN. 283 
number should be so small seems at first thought strange, when it is remembered that 
the low elevations just east of the mountains are unmistakably middle province in the 
character of their avifauna. 
With reference to the geological structure of the Deschutes Basin and other areas 
just east of the Sierra and Cascade Ranges, Dr. Newberry affirms their intimate con¬ 
nection with the Rocky Mountain Desert; nor in considering the flora and fauna of 
these areas does he fail to note many examples that serve to indicate their closer affin¬ 
ity to the Rocky Mountain region than to the Pacific. 
In the case of birds the physical obstacles to be surmounted, formed by the high 
mountain crests, although doubtless not without effect, have probably far less to do 
with the absolute limitation of species than has the check ottered by the conditions of 
a different climate, with the consequent change in plant and insect life which this im¬ 
plies. The region west of the mountains has a large mean annual rainfall, the effect 
of which upon plant and auimal life is further maintained during the dry season by 
the accession of moisture from the ocean; but the moisture-laden winds are finally 
robbed as they pass eastward over the summits of the mountains, and they reach the dis¬ 
tant interior dry and without life-giving power. As a consequence, and in connec¬ 
tion with its volcanic character, the interior plateau country, almost rainless during 
the summer, is, for the most part, dry and barren in the extreme. The oases, in fact, 
in this general desert are limited to the areas which, through geological disturbances, 
have been uplifted to a sufficient height to intercept cloud moisture; and, in addi¬ 
tion, the banks of the streams, which afford restricted ground for the growth of vegeta¬ 
tion, and through it a home for animal life. With the above well-defined differences 
of climate, it is not surprising that a corresponding change in the flora and fauna of 
the two regions is observable. 
Although, as stated, the Sierra and Cascade Ranges present in the main a continuous 
chain, its continuity is interrupted in several places, the Columbia, the Klamath, and 
the Pitt Rivers breaking through its wall in their progress to the Pacific. Nevertheless, 
the presence of the natural passes thus afforded does not appear to have a marked 
effect upon the distribution of birds and mammals, if, indeed, it is to be detected at all. 
The narrowness of their canons, flanked as they are in the case of the Columbia by 
extremely dense coniferous woods, and of the others by an inhospitable desert-like 
country, would probably have an effect in preventing the passage of species back and 
forth, were there no other existing cause. But, as remarked before, probably the main 
obstacle is to be found in the different climates of the two regions. Those species 
habituated to the warmer, more equable, and moist climate of the Pacific side, and to 
a country covered with profuse vegetation, would naturally be repelled by the harsher 
climate and dry, desolate country to the eastward; while such as are inured to the 
latter conditions would find the former equally unattractive. As further evidence that 
it is chiefly the climate and the conditions resulting therefrom that limit the range of 
birds, and not the mere physical barriers offered by mountain chains, it may be remarked 
that by no means the same amount of difference is to be observed between the birds of 
the regions that lie contiguous to the eastern and western slopes of the Rocky Mountains 
that is to be noted here. And we may safely infer that the very marked faunal simi¬ 
larity of the latter sections is largely due to the corresponding similarity of climates, 
the Rocky Mountains appearing to ffiave little or no effect in limiting the range of 
birds and mammals. 
In a region possessing the forbidding aspect of that to the east of the Sierras, it 
might be inferred that the sum total of bird life would be rather small. In general, 
this is true; but along the streams there is usually to be noticed a rather marked con¬ 
centration of species, while in some favored localities the number also of individuals 
is great. The mountainous districts, with their heavy growth of conifers aud decidu¬ 
ous shrubs, as well as their profusion of annual plants, which up to a certain limit ac¬ 
company the increased amount of rainfall, form the home of numerous species not 
found elsewhere. In fact, the more favorable localities in the mountains form the best 
collecting grounds for the naturalist. 
A somewhat special type of country was entered during the past season in the Des¬ 
chutes River region, the general watershed of which stream has elsewhere been termed 
the “ Deschutes Basin.” As it is peculiar in some of its aspects, this region merits brief 
mention. With a general elevation of about 4,000 feet above sea-level, much of this area 
is covered by a uniform growth of the yellow pine (Pinus ponderosa), which appears to 
thrive wonderfully well in the light soil of pulverized pumice. From the fact that the 
water supply is extremely limited and occurs for tbe most part only as small spriugsor 
in water-holes, very few shrubs and plants are able to maintaiu existence, and a hardy 
kiud of grass alone covers the soil with a scanty growth. So far as birds are concerned, 
it would be difficult to realize a more complete type of desert than is here presented. 
For days in succession, I have ridden through these forests, the mules each step sink¬ 
ing above the fetlock in the treacherous dust, which, rising in clouds, marked the 
route of the party as by a column of smoke, scarcely seeing or hearing a bird. The 
rare note of a woodpecker or nuthatch, or the chirpings of a few venturesome snow- 
