S2 Page 68

Collector: Grinnell - 1925
Location: Mineral to Red Bluff and back
Date: July 6
Page Number: 2521

A western House Wren, again, in snow-brush
near camp, singing sketchily. Two Brewer
Blackbirds flew over.

Today, went to Red Bluff and back - an impressive
lesson in the variation of temperature inversely
with altitude! The dryness below 3500 feet was
also impressive; and the blueness of all the perennial
vegetation (ceanothus cuneatus, Douglas Oak, and
digger pine) in the Upper Sonoran. That zone
might be called the "blue zone", Transition the
"light green zone", Canadian the "dark green zone".
These color-tone differences indicate, of course,
fundamental conditions affecting physiological
processes in ^^the plants - temperature of growing
season, length of growing season, dryness of air,
soil-water supply, and perhaps others (such
as insolation).

Four or five miles east of Red Bluff saw
the usual Raven, whose headquarters I guess
are somewhere around Tuscan Buttes. Western
Kingbirds were most noticeable of birds in the
immediate precincts of Red Bluff - noisy despite
the intense heat of midday - indeed; indeed,
the ^^bickering notes of this species are inseparable,
associated in my mind with the summer
heat of the Great Valley. Of considerable
interest was our frequent interrupting of
Turkey Vultures along the highway, all the