_Turdus swainsoni_, CAB. Tschudi, Fauna Peruana, 1844-46,
188.—? SCLATER & SALVIN, Ibis, 1859, 6 (Guatemala).—SCLATER, P.
Z. S. 1858, 451 (Ecuador); 1859, 326.—IB. Catal. 1861, 2, no.
11.—BAIRD, Birds N. Am. 1858, 216; Rev. Am. B., 1864,
19.—GUNDLACH, Cab. Jour. 1861, 324 (Cuba).—IB. Repert. 1865,
229.—PELZELN, Orn. Brazil. II. 1868, 92 (Marambitanas, Feb. and
March).—LAWR. N. Y. Lyc. IX, 91 (Costa Rica).—RIDGWAY.—
MAYNARD.—SAMUELS, 152.—COOPER, Birds Cal. 6.—DALL & BANNISTER.
_Turdus minor_, GMELIN, Syst. Nat. I, 1788, 809 (in part). _Turdus
olivaceus_, GIRAUD, Birds L. Island, 1843-44, 92 (not of LINN.).
_(?) Turdus minimus_, LAFRESNAYE, Rev. Zoöl. 1848, 5.—SCLATER, P.
Z. S. 1854, 111.—BRYANT, Pr. Bost. Soc. VII, 1860, 226
(Bogota).—LAWRENCE, Ann. N. Y. Lyc. 1863. (Birds Panama, IV, no.
384.)
SP. CHAR. Upper parts uniform olivaceous, with a decided shade of
green. The fore part of breast, the throat and chin, pale
brownish-yellow; rest of lower parts white; the sides washed with
brownish-olive. Sides of the throat and fore part of the breast with
sub-rounded spots of well-defined brown, darker than the back; the
rest of the breast (except medially) with rather less distinct spots
that are more olivaceous. Tibiæ yellowish-brown. Broad ring round the
eye, loral region, and a general tinge on the side of the head, clear
reddish buff. Length, 7.00; wing, 4.15; tail, 3.10; tarsus, 1.10.
HAB. Eastern North America; westward to Humboldt Mountain and Upper
Columbia; perhaps occasionally straggling as far as California; north
to Slave Lake and Fort Yukon; south to Ecuador and Brazil. Cuba,
GUNDLACH; Costa Rica, LAWR.
Specimens examined from the northern regions (Great Slave Lake,
Mackenzie River, and Yukon) to Guatemala; from Atlantic States to East
Humboldt Mountains, Nevada, and from intervening localities. The
extremes of variation are the _brownish_-olive of eastern and the
clear _dark_ greenish-olive of remote western specimens. There is no
observable difference between a Guatemalan skin and one from Fort
Bridger, Utah.
HABITS. The Olive-backed Thrush, or “Swamp Robin,” has very nearly the
same habitat during the breeding season as that of the kindred species
with which it was so long confounded. Although Wilson seems to have
found the nest and eggs among the high lands of Northern Georgia, it
is yet a somewhat more northern species. It does not breed so far
south as Massachusetts, or if so, the cases must be exceptional and
very rare, nor even in Western Maine, where the “Ground Swamp Robin”
(_T. pallasi_) is quite abundant. It only becomes common in the
neighborhood of Calais. It is, however, most widely distributed over
nearly the entire continent, breeding from latitude 44° to high Arctic
regions. It winters in Guatemala and southward as far as Ecuador and
Brazil.
In its habits this thrush is noticeably different from the _T.
pallasi_, being much more arboreal, frequenting thick woods; rarely
seen, except during its migrations, in open ground, and seeking its
food more among the branches of the trees.
Mr. Ridgway found this species very abundant among the Wahsatch
Mountains, where it was one of the most characteristic summer birds of
that region. It was breeding plentifully in the cañons, where its song
could be heard almost continually. It inhabited an intermediate
position between _T. auduboni_ and _T. fuscescens_, delighting most in
the shrubbery along the streams of the cañons and passes, leaving to
the _T. auduboni_ the secluded ravines of the pine regions higher up,
and to the _T. fuscescens_ the willow thickets of the river valleys.
He did not meet with it farther west than the East Humboldt Mountains.
The song, in his opinion, resembles that of the Wood Thrush (_T.
mustelinus_) in modulations; but the notes want the power, while they
possess a finer and more silvery tone.
The song of this species has a certain resemblance to that of _T.
pallasi_, being yet quite distinct, and the differences readily
recognized by a familiar ear. It is more prolonged; the notes are more
equal and rise with more regularity and more gradually, are richer,
and each note is more complete in itself. Its song of lamentation when
robbed of its young is full of indescribable pathos and beauty,
haunting one who has once heard it long after.
When driven from the nest, the female always flies to a short distance
and conceals herself; making no complaints, and offering no
resistance.
These birds, in a single instance, have been known to reach Eastern
Massachusetts early in April, in an unusually early season, but they
generally pass north a few weeks later. They make no prolonged stay,
and are with us rarely more than three or four days. Their return in
the fall appears to be, at times, by a more inland route. They are
then not so numerous near the coast, but occasionally are abundant.
Their nests in Nova Scotia, wherever observed, were among the thick
woods, on horizontal branches of a forest-tree, usually about five
feet from the ground. Those observed in the Arctic regions by Mr.
Kennicott were frequently not more than two feet from the ground.
The nests average about four inches in diameter and two in height, the
cavity being three inches wide by about one and a half deep. They are
more elaborately and neatly constructed than those of any other of our
thrushes, except perhaps of _T. ustulatus_. Conspicuous among the
materials are the _Hypnum_ mosses, which by their dark fibrous masses
give a very distinctive character to these nests, and distinguish them
from all except those of the _T. ustulatus_, which they resemble.
Besides these materials are found fine sedges, leaves, stems of
equisetaceous plants, red glossy vegetable fibres, the flowering
steins of the _Cladonia_ mosses, lichens, fine strips of bark, etc.
The eggs, which are four or five in number, exhibit noticeable
variations in size, shape, and shades of coloring, bearing some
resemblance to those of _T. ustulatus_ and to the eggs asserted to be
those of _T. nanus_, but are sufficiently distinct, and are still more
so from those of _T. aliciæ_. They range in length from .83 to .94,
with a mean of .88, their mean breadth is .66, the maximum .69, and
the minimum .63. Their ground color is usually bluish-green, sometimes
light blue with hardly a tinge of green, and the spots are of a
yellowish-brown, or russet-brown, or a mixture of both colors, more or
less confluent, with marked variations in this respect.
Turdus swainsoni, var. ustulatus, NUTTALL.