_Vireo_, VIEILL. Ois. Am. Sept. I, 1807, 83. (Type, _Muscicapa
noveboracensis_, GM.)
No great violence will be done by considering all the American Vireos
as belonging to one genus, divisible into three subgenera, as, however
different the extremes of the series may be from each other, the
gradation is quite complete.
The North American species take a wide range during their southern
winter migration, only paralleled in this respect by the
_Sylvicolidæ_; they do not visit the West Indies, save as very rare
stragglers to Cuba (_V. olivaceus_, _solitarius_, _flavifrons_, and
_noveboracensis_). They all have a melodious song, and, so far as
known, make a deep nest, suspended by its upper edge between the forks
of a horizontal twig. The eggs are white, generally with a few reddish
or brown blotches.
Quite a number are characterized by having the eyes white, red, or
yellow.
Subgenera.
Vireosylvia. Bill compressed, narrow; culmen and commissure
straight, the tip abruptly curved (or, if this is not the case,
there is no trace of light bands on the wing; see section “_b_”).
Superciliary stripe continued back to the occiput. No trace of
light bands on the wing. No conspicuous ring round the eye.
_a._ No spurious primary. Bill compressed, its tip abruptly
hooked; culmen and commissure straight. Crown decidedly more
ashy than the back …
Sp. _flavoviridis_, _barbatulus_, _olivaceus_, _philadelphicus_.
_b._ An acute spurious primary. Bill depressed, the tip only
slightly hooked; culmen slightly curved. Crown scarcely more
ashy than back … Sp. _gilvus_.
Lanivireo. Bill compressed, stout; culmen arched from the base,
commissure curved. Superciliary stripe stopping at posterior
angle of the eye and curving under it, enclosing the eye in a
conspicuous orbital ring, interrupted only in front. Two
conspicuous white bands on the wing.
_a._ No spurious primary … Sp. _flavifrons_.
_b._ With an acute spurious primary … Sp. _solitarius_, _plumbeus_.
Vireo. Bill stout, scarcely compressed, sub-cylindrical. First
primary not spurious, or, if so, not acute.
_a._ Two conspicuous light bands on wing …
Sp. _atricapillus_, _noveboracensis_, _huttoni_.
_b._ One distinct light band on wing, and this not sharply
defined, the anterior one being almost obsolete …
Sp. _belli_, _pusillus_, _vicinior_.