THE BIRDS
YELLOWTHROATS. Geothlypis trichas (Linnaeus)35
Field characters.About
half size of Junco. Adult male: Forehead and face crossed by a broad
band or mask of black, bounded above by white; throat and most of under
surface clear yellow; upper surface of body yellowish brown. (See pl.
9i). Female and young: Yellowish brown above, yellowish white
beneath. An active yet reclusive species. Voice: Song of male a
set theme given three or four times in slow rhythm with rather insistent
delivery, wretch'-et-y, wretch'-et-y, wretch'-et-y; call note a
sharp yet hoarse-sounding tchack.
Occurrence.Common
resident at Snelling and below Lagrange (subspecies scirpicola).
Transient along both flanks of Sierra Nevada and summer visitant at Mono
Lake (subspecies occidentalis).35 Lives low in tule
marshes and shrubbery bordering streams. Solitary or in
pairs.
35Two closely similar
subspecies of Yellowthroat occur in the Yosemite section.
WESTERN YELLOWTHROAT, Geothlypis
trichas occidentalis Brewster, a smaller duller colored race
summering in the Great Basin and the Northwest, a transient along both
flanks of the Sierra Nevada, and a summer visitant about Mono Lake. It
has occurred in the fall migration at Smith Creek, east of Coulterville,
and in spring and fall in Yosemite Valley.
TULE YELLOWTHROAT, Geothlypis
trichas scirpicola Grinnell, a larger, longer tailed and more
brightly colored subspecies, resident in the San Joaquin Valley and in
southern California, was found in both winter and summer at Snelling and
near Lagrange.
The Yellowthroats are birds of marshy places and so
are found in numbers at both ends of the Yosemite section, but they are
of only casual occurrence elsewhere in the region. Individuals pass
through the western foothill country during the migrations. A male bird
was noted by us May 29, 1911, in Yosemite Valley near Stoneman Bridge;
and two birds were noted in Yosemite Valley on the morning of September
29, 1917 (Mailliard, 1918, p. 16). The lack of suitable cover in the
form of dense thickets of willow or of tules probably accounts for the
failure of the birds to remain there throughout the summer.
The Yellowthroats found at Snelling and Lagrange
(subspecies scirpicola) are the only really resident members of
the whole warbler family in the Yosemite section. Suitable forage and
cover are evidently sufficient there at all seasons; they remain in full
numbers throughout the colder portion of the year. At Snelling 10 were
noted in tangles of blackberry, nettles and willows during a 2-1/2-hour
census on January 6, 1915. Eight were recorded in similar cover at that
place during a 3-hour trip on May 26; and on May 29 the same year not
less than 18 of the birds were noted during an hour and a half in
particularly favorable country.
Near Lagrange, on May 7, 1919, a pair was observed in
the dense cover of green and dried tules bordering a small pond; the
male was singing at short intervals, while the female, glimpsed but
once, was carrying nest material.
The birds observed about Mono Lake
(occidentalis) in 1916, even as late as the last of May, were not
yet fully established for nesting. In the fall of 1915 one individual
was obtained, September 20, at the shore of Mono Lake nearest Mono
Craters.
In the western part of the Yosemite region the Tule
Yellowthroat lives in close association with the Least Vireo,
individuals of the two species often being seen, in summer, working
through the same clump of vegetation. No other warbler of the lowlands
lives so close to the ground. The Yellowthroats rarely go even so far
as 6 feet above the ground and their nesting and foraging activities
usually involve a vegetational stratum of only half this depth.
|