346 
PASSERIFORMES 
626. Philadelphia Vireo. le vireo paresseux. Vireo ■philadelphicus. L, 4 -75. 
Almost exactly similar in size, form, and coloration to the Warbling Vireo (Plate LXIII A), 
but more generally suffused with 
yellow on the breast, flanks, and under- 
parts. 
Distinctions. The Philadelphia is 
likely to be mistaken only for the 
Warbling Vireo, but is yellower below 
and can almost always be separated by 
the first visible primary being nearly 
as long as the next (Figure 429) in- 
stead of being reduced to rudimentary 
conditions (Compare with Figure 430). 
Field Marks. In life it looks like a Warbling Vireo with unusually yellow under- 
parts. The light eye-brow stripe is usually a little stronger than in that species, and 
may at times suggest the head of a small Red-eyed Vireo. 
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. 
Underwing surface of Philadelphia Vireo, first 
primary long; natural size. 
627. Warbling Vireo. le vireo melodieux. Vireo gilvus. L, 5-80. Plate LXIII 
A. A small vireo, looking like a dull, grey-green warbler. Above: dull grey, slightly 
olive, especially on rump. White below from throat to tail-coverts. A faint, light eye- 
brow-line. 
Distinctions. One of the dullest, most inconspicuously coloured birds we have, without 
any special detail in marking except the soft eye-brow fine. In general most like the 
Tennessee Warbler, but duller coloured; less green on back and less grey on crowm, and 
with vireo hooked bill ( See Figure 426). 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 almost finally determinative 
character of this vireo, however, is the rudimentary condition of the first primary, barely 
three-quarters of an inch long (Figure 430, compare with 429). 
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,, 
faint eyebrow stripe. Rather slower in 
action and less agile than a warbler. 
Separated from the other vireos by 
smaller size and duller coloration, 
especially 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 firmly interwoven and 
lined with pine needles and hairs. 
Distribution. Temperate North America. In Canada, across the Dominion, north 
to Mackenzie Valley. 
Figure 430 
Underwing surface of Warbling Vireo, first 
primary very short; natural size. 
SUBSPECIES. Divided into Eastern and Western forms. The Eastern Warbling 
Vireo (le Vireo melodieux de l'Est) Vireo gilvus gilvus ranges west to the mountains. The 
Western Warbling Vireo (le Vireo melodieux de 1’Ouest) Vireo gilvus 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 differ- 
entiate that the distinction of the two ranges has not been well defined. 
The Warbling Vireo, hidden in the leafy tree tops, 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. 
