118 VIREONID®, VIREOS.—GEN. 53. 
six genera and nearly seventy recorded species, of which about five-sixths appear 
to be genuine. The typical and principal genus, Vireo, containing nearly thirty 
species, is especially characteristic of North America, though several species occur 
in the West Indies and Central America; one genus and species, Laletes osburni, 
is exclusively West Indian; the rest — Cyclarhis, Hylophilus, Vireolanius, and 
Neochloe— are, with one exception, South and Central American. In further illus- 
tration of the characters of the group, I offer some remarks under the head of the 
only genus with which we have to do in the present connection. 
53. Genus VIREO Vieillot. 
The numerous species of this genus have been divided into several groups, but 
no violence will be done by considering them all as Vireo —in fact, it is difficult to 
do otherwise. For even the seemingly substantial division into two genera, ac- 
cording as there is an evident spurious first primary or apparently none, separates 
species, like gilvus and philadelphicus, hardly otherwise specifically distinguishable ; 
while another division into two genera, according to shape of the wings and length 
of the spurious first primary or its absence, is subject to some uncertainty of deter- 
mination, and unites species, like olivaceus and jflavifrons, most dissimilar in other 
respects. The fact is, that almost every single species of Vireo has its own peculiar 
form, in shape of bill, proportions of primaries, etc., and these details cannot well 
be considered as of more than specific value. These slight differences are perfectly 
tangible and surprisingly constant, and render the deter- 
mination of the species comparatively easy, though these 
birds bear to each other a close general resemblance in 
size and color. They are all more or less olivaceous 
above, sometimes inclining to gray or plumbeous, with 
the crown either like the back, or else ashy—in one 
species, however, brown, and in another black; and white 
or whitish below, usually more or less tinged with yellow. 
The coloration is very constant, the sexes being indistin- 
cuishable, and the young differing little, if at all, from the adults. All are small 
birds — about 5 or 6 inches long. As a group the student will probably have no 
difficulty in recognizing them by the foregoing diagnosis, as the character of the 
feet seems to be peculiar, among North American birds, and is at any rate 
diagnostic when taken in connection with the character of the bill—all those 
Oscines, as wrens, creepers, or titmice, that show much cohesion of the toes, 
having an entirely different bill. The bill of Vireo may be described as resembling 
that of a shrike in miniature —it is hooked and notched distinctly at the end, and 
there is sometimes a trace of a tooth behind the notch, and of a nick in the under 
mandible too. Some of the weaker-billed species might be carelessly mistaken for 
warblers— but there is no excuse for this, nor for confounding them with any of 
the little clamatorial flycatchers. 
The Vireos were long supposed to possess either nine or ten primaries. But that 
the important character of number of primaries —one marking whole families as 
we have seen—should here subside to specific value only, seemed suspicious; and 
the fact is, as announced by Baird (Review, pp. 160,325) that all the species 
really have ten, only that, in some instances, the first primary is rudimentary and 
displaced, lying concealed outside the base of the second quill. 
The North American species are distributed over the temperate portions of this 
Fic. 58. Warbling Vireo. 
