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.