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spiders, and other insect forms are also taken. The food of the species 
throughout the year is regarded by the United States Biological Survey 
as being beneficial in the ratio of 4 to 1. 
FAMILY—VIREONID®. VIREOS OR GREENLETS. lL, 4-75-6-23. 
General Description. Small, warbler-like birds generally coloured in greens and white 
with more or less yellow in softly suffused masses and without much definite marking. 
The bill is perceptibly notched and hooked at the tip much like that of the Shrike (Figure 
56, page 56), but is on a much smaller and much lighter scale. 
Distinctions. The Vireos are most apt to be mistaken for warblers which in habit, 
size, and general coloration they resemble. The bills, however, are stouter, more strongly 
arched on the culmen, higher for the width, and more evidently hooked and notched 
at the tip. The Yellow-breasted Chat has a bill that might answer this description 
in outline, but it is not hooked nor has it any indication of notch at tip. 
Field Marks. In addition to specific markings, which form the best guide to 
species, the Vireos can be recognized by their warbler-like habits but slower and more 
sluggish movements, peering under leaves and gleaning from the branches and twigs with 
less activity. 
The Vireos constitute a small family peculiar to America. Three 
genera occur in Canada, represented by six species. 
Economic Status. Economically the Vireos can be treated together 
as they are similar in their food habits. Their food consists of 91 per cent 
of insects and the remainder of fruits. The latter are almost without 
exception wild varieties. The insects taken are among the most harmful, 
including scales and other close lying species that no birds but the careful, 
close-peering Vireos ordinarily seek. They are among our more useful 
birds. : 
624. Red-eyed Vireo. PREACHER-BIRD. TEACHER. FR.—LE VIREO AUX YEUX 
RrouGES. Vireosylva olivacea. L, 6-23. Plate XXXVIII B. 
Distinctions. The Red-eyed can be distinguished from other Vireos by its superior 
size, the lack of yellow, the grey confined to the crown, and the white eyebrow line bordered 
with dark both above and below. The iris is red, but this can only be seen on very close 
examination. 
Field Marks. The markings of the face of the Red-eyed makes the best field mark. 
The white eyebrow bordered with darker colour and the lower line through the eye can 
usually be seen as the bird peers through the leaves at the intruder. 
Nesting. Suspended from between the forks of a small branch 5 to 15 feet above the 
ground in pensile nest or hanging-cup, woven of strips of bark, dead wood fibres, paper, 
plant down, or birch bark lined with fine materials. 
Distribution. North America to near the limit of trees. 
The Red-eyed Vireo is one of the commonest frequenters of our 
groves and woods. Its song, a leisurely repetition of slight variants of the 
same phrase with pauses between, and continued ad libitum, can be heard 
in the tree tops almost anywhere in Canada and has given the species the 
name of Preacher-bird. 
626. Philadelphia Vireo. FR—LE VIREO DE PHILADELPHIE. Vireosylva phil- 
adelphica. L, 4-75. Almost exactly similar in coloration to the Warbling Vireo (Plate 
XX XIX A) but more generally suffused with yellow on breast, flanks, and below. 
Distinctions. The Philadelphia can always be separated from the Warbling Vireo by 
the length of the first primary feather. In this species it is nearly as long as the second, 
whereas in the Warbling it is reduced to a rudimentary condition and is barely three- 
quarters of an inch in length. 
Field Marks. In life it looks like a Warbling Vireo with unusually yellow breast and 
underparts. 
