312 
Nesting. Nest pensile, suspended from a branch, of fibres and birch-bark. 
Distribution. Eastern North America. In Canada, west to Alberta and north to 
lake Athabaska. 
A rather rare little Vireo, too inconspicuous to be seen or recognized 
by the casual observer. 
627. Warbling Vireo (Including Western Warbling Vireo). Vireosylva gilva. L, 
5*80. Plate LXVII A. A small Vireo, looking like a dull, grey-green Warbler. Above: 
dull greyj slightly olive, especially on rump. White below from throat to tail-coverts. 
A faint, light eyebrow-line. 
Distinctions. One of the dullest, most inconspicuously-coloured birds we have, withou 
any special detail in marking except the soft superciliary line. In general, most like the 
Tennessee Warbler, but duller coloured; less green on back and less grey on crown, and 
with Vireo hooked bill ( See Figure 277). The even, unmarked coloration will separate 
it from any other Vireo except the Philadelphia. The lack of yellow overwash on throat 
and below will usually be diagnostic from that species. The finally determinative character 
of this Vireo, however, is the rudimentary condition of the first primary, barely three- 
quarters of an inch long (Figure 279 compare with 278). 
Field Marks. Like a small, dull-greenish or greyish Warbler, but more evenly and 
less conspicuously coloured than any of them, the only pattern detailed being a soft, 
f ain t eyebrow stripe . Rather slower in 
action and less agile than a Warbler. 
Separated from the other Vireos by 
smaller size and duller coloration, 
expecially the lack of yellow below and 
the faintness of the eyebrow stripe. 
Nesting. Nest pensile, suspended 
from forks of small branch, composed 
of fine bark strips and plant fibres, 
smoothly and firmlv interwoven and 
lined with pine needles and hairs. 
Distribution. Temperate North America. In Canada, aero® the Dominion, north 
to Mackenzie valley. 
SUBSPECIES. Divided into Eastern and Western forms. The Eastern Warbling 
Vireo Vireosylva gilva gilva ranges west to the mountains. The Western Warbling 
Vireo Vireosylva gilva swainsoni , declared to be slightly smaller and darker, occupies 
British Columbia and some of the more eastern territory to the north in Alberta and 
Mackenzie. The two races are so difficult to differentiate that the distinction of the two 
ranges has not been well defined. 
The Warbling Vireo, hidden in the leafy treetops, is more often heard 
than seen. Its song is unlike that of the Red-eyed or even its closer relative 
the Philadelphia, being a rather long, continuous warble, which in summer 
is one of the most characteristic sounds in its habitat. 
628. Yellow- throated Vireo. Lanivireo flamfrons. L, 5-95. Slightly smaller than 
the Red-eyed and larger than the Warbling Vireos. Head, cheeks, and back greenish; 
ramp and fail slaty; breast and throat bright yellow; white below. Wings with two 
distinct bars. 
Distinctions. The bright yellow of the breast of this species is distinctive amongst 
the Vireos. It has white wing-bars; the Solitary is the only other Vireo within its range 
that has this character. In general coloration, the Yellow-throated Vireo is most like the 
Pine Warbler, but has considerably more white on the underparts and the yellow ends 
almost sharply at the breast-line. The finely hooked bill (Figure 277), of course, will 
distinguish it as a Vireo. 
Field Marks. The bright yellow on throat will prevent confusion with any other 
Vireo, and the larger amount of white and the decided termination of the yellow breast 
against it will separate it from the Pine Warbler. Its voice is much like that of the Red- 
eyed, but the notes follow each other more slowly. 
Nesting. Nest pensile, from fork of branch, of strips of bark, plant fibres, etc., lined 
with fine grasses and covered externally with lichens and spider webs. 
Distribution. Eastern North America. In Canada, only in the most southern parts, 
west to and including southern Manitoba. 
Figure 279 
Underwing surface of Warbling Vireo, first 
primary very short; natural size. 
