Imperial Valley press., 1914-04-02


California. side, and II on the Ariz-
ona side. From each of the base
camps as center, hunting and trap
ping We're carried on as far radi-
cally as proved practicable. 1t was
the effort of the explorers to test
every sort of ground available, from
the tule covered swamps and the will
low thickets along the river to the
catclaw thickets of the desert ra-I
vines and the spiny shrubs of the
rocky hills. In all, II different asso-
Citations or groups of plant growth
were found in the desert bordering
the river. Each association pos
sessed certain birds and small NAM
mails dependent upon it for food or for
shelter or for both. One of the most
interesting associations studied was
the Saguaro association, where the
Saguaro, or giant cactus, usually sup
posed to be confined to Arizona, was
found upon the California side of the
river. AS the explorers foated down
the Colorado river, just below the
point where the Bill Williams river
emptiesf into it, they beheld the huge
stems of the giant cactus studding
the sky line on both sides of the
river. A landing was made on the
California side and several saguaros
examined for nesting sites of birds.
1t was found that in the tall stems
Of the thorny cactuses many wood
peckers had excavated safe retreats
in which to rear their young. Other
kinds of birds, recognizing the safety
of these locations, had taken advan
tage of deserted woodpecker holes
and made their nests in them. One
giant cactus was found to harbor a
nest of Gila woodpecker and that
OF an ash -throated fycatcher, while
in another trunk nearby a screech
owl had made her home three feet
above that of a brood of gilded flick
ors.
In the willow association bird life
was found to be most abundant and
mammals fewer than elsewhere. This
scarcity of terrestrial animals the OBJ
servers believed to be due to the fact
that here the ground is inundated at
high water annually, and not only
would ground dwelling mammals be
drowned, but their food supply would
be cut off for many days at time.
One main object of the expedition
was to study the effect of the Colo
RADIO river as a highway for the dis
persal of some species of animals
and as an absolute barrier for 9TH
ers.
To bats and birds the river, of
course, does not act as a barrier,
and larger mammals such as even
the mountain lion and wild cat were
found to swim from side to side, as
necessitated by search for food.
Of the 43 kinds of mammals found
along the river and on the nearby
desert II were found to be completely
restricted to one side or the other OF
the river. In no instance was species
which dwelt close to the waters edge
found to be restricted to one side,
and DR.. Grinnell suggests that these
species are occasionally transported
hack and forth across the river on
driftwood or by other means, thus
maintaining the identity of the spc-
lies on the two sides. One species, for
instance, a mouse, repeatedly CAM
board the scow when it was moored
beside the bank for the night.
Among the species restricted by the
river were the desert chipmunks, dis
tinct species of which occupied op-
posite sides of the river. These ami
mails live upon the rocky hillsides
some distance from the river and
since the climate and plants upon the
two sides are alike it is supposed that
tha fx,o binds of obipnupkS now nrpS