_Vireo pusillus_, COUES, Pr. A. N. Sc. Phila. 1866.—BAIRD, Rev. Am.
B. 360.—ELLIOT, Illust. Birds N. A. I, vii.—COOPER, Orn. Cal. 1,
1870, 124. _? Vireo belli_, COOPER, Pr. Cal. Acad. 1861, 122 (Fort
Mohave).
[Line drawing: _Vireo pusillus._
31893]
SP. CHAR. Somewhat similar in general appearance to _Vireosylvia
gilva_ and _swainsoni_, but smaller. Bill very small; tarsi
lengthened. Wings about equal to the tail, which is lengthened,
graduated, and with the feathers narrow and pointed. Exposed part of
first primary about half that of the second, which is intermediate
between seventh and eighth; the fourth and fifth longest.
Above grayish-ash, with a tinge of olive behind. Beneath, including
the inside of the wings, white, with a soiled tinge on the sides of
the throat and across the breast. Axillars and flanks exhibiting a
faint trace of greenish-yellow. Eyelids and a short line from the
nostrils to the eye whitish; no other stripe apparent. A dusky loral
spot. Primary coverts edged indistinctly with whitish, producing an
obscure band (a second on the middle coverts hardly appreciable).
Quills and tail-feathers edged externally with pale grayish-olive, the
innermost secondaries with whitish. Bill dusky above, whitish beneath.
Legs plumbeous. Iris of two specimens marked as “light brown,” of
another as “rufous.”
The details of structure taken from No. 23,785, of color from No.
23,788: Length, of 23,785 ♂, 4.80 when fresh, of skin, 4.25; wing,
2.25; tail, 2.25; bill above, .37; tarsus, .73; middle toe and claw,
.50; hind toe and claw, .42. First quill, .70; second, 1.40; longest
(fifth), 1.64. (Cape St. Lucas.)
HAB. Cape St. Lucas; San Diego; Fort Mohave, and Arizona; Sacramento,
California (RIDGWAY).
This species scarcely needs comparison with any other, except,
perhaps, _V. pallens_ of Middle America, which, however, besides
belonging to _Vireonella_, and not _Vireo_, as restricted, differs in
many minor, but no less essential points. The coloration of the two is
remarkably similar, but _pusillus_ has only one indistinct band on the
wing, instead of two sharply defined ones. The bill is much smaller,
and the tail longer, than in _pallens_. _V. belli_ is less ashy above
and less pure white beneath, the sides much more yellowish; the wing
is also longer, and the tail much shorter. _V. vicinior_ is much
larger, with the wing longer than the tail, instead of shorter; the
ash above has a bluish instead of a greenish cast; the lores are
wholly grayish-white, etc.
HABITS. The Least Vireo is a recently described species of its genus,
and one in regard to whose history comparatively little has been
ascertained. It was first met with at Cape St. Lucas by Mr. Xantus,
and described by Dr. Coues in 1866. Dr. Coues assigns as its habitat
Lower and Southern California, Sonora, and Arizona, at least as far
north as Fort Whipple. Dr. Cooper also found it at Fort Mohave. Dr.
Coues met with it fifty miles south of Fort Whipple, where he found it
breeding abundantly. He gives no information in regard to its habits.
Dr. Cooper states that he found it rather common along the upper part
of Mohave River, in June, 1861; and in the following spring, about
April 20, they began to arrive at San Diego in considerable numbers.
In its habits Dr. Cooper thinks it greatly resembles _V. gilvus_,
though it differs entirely in its song. The notes of those that he
heard singing resembled very much those of the Polioptilas uttering a
quaint mixture of the notes of the Wrens, Swallows, and Vireos. They
also seem to possess more or less of imitative powers. At Sacramento
he saw and heard, in the willows along the river, individuals which,
from their peculiar notes, he had no doubt were of this species, but
he did not verify his conjectures. His suppositions were confirmed
later by the observations of Mr. Ridgway, who states that he found
these birds the most abundant as well as the most characteristic
Greenlet in the vicinity of Sacramento. It is a species, he adds,
easily recognized, being in all respects quite distinct from any
other. The character of its notes, as well as its habits, show it to
be a true Vireo. Its song, though weaker, bears a great resemblance to
that of the White-eyed. A nest of this species was found by him near
Sacramento. It was placed about three feet from the ground, in a low
bush in a copse of willows. Like all the nests of this genus it was
pensile, being attached to and suspended from the twigs of a branch.
Two nests of this interesting species were also obtained near Camp
Grant, Arizona, in 1867, by Dr. E. Palmer. They are wrought like all
the nests of this kind, below the small forked branches of a tree,
suspended from the extremity of its twigs. They each have a diameter
of about three and a half inches, a height of two, with a cavity an
inch and a half deep and two wide. The external portion, like the
nests of the _V. belli_, is wrought with woven hemp-like vegetable
fibres, strongly bound around the ends of the twigs and covering the
entire exterior. Within this is placed a strong, firmly made basket,
composed of slender strips of bark and long, fine, and flexible
pine-needles, with a lining of finer materials of the same. In one of
these nests there were three eggs of the Vireo, and one of a
_Molothrus_ (_obscurus?_). The former were of a bright crystalline
whiteness, marked with very minute and hardly discernible spots of
red, and measure .69 by .56 of an inch. The egg of the _Molothrus_,
except in its much smaller size, is hardly distinguishable from those
of the common _M. pecoris_, and measures .75 by .56 of an inch.
In the other nest were also three eggs of the Vireo. They correspond
in size, but are much more distinctly marked with larger spots of a
dark red and reddish-brown. In this nest there is a somewhat larger
proportion of fine strips of inner bark, and mixed with these are also
a few silky insect cocoons, by means of which the nest is firmly bound
around the twigs from which the whole is suspended.
Vireo vicinior, COUES.