The song is a series of chips, introduced by the syllables wee-see, wee-see, wee-see.
ORANGE-CROWNED WARBLER
Vermivora celata celata (Say)
Description.—Olive-green above; crown with more or less concealed dull orange patch, not easily seen in the field; underparts and obscure ring about eye dull yellow; sides irregularly streaked with olive-green; sexes similar. Young birds: Duller. Length: 5 inches.
Range in Pennsylvania.—The Orange-crown is one of our little-known warblers which may be considerably commoner than we suppose. It occurs as a migrant in May and September, and is to be found chiefly in swampy situations, principally among alders.
The song, which is not often heard in Pennsylvania, according to my experience, is considerably like that of a Nashville or Tennessee Warbler, being a series of chips, but the tempo is different. All such songs should be thoroughly investigated to make certain some rare bird is not passed by. (See illustration, [page 131].)
TENNESSEE WARBLER
Vermivora peregrina (Wilson)
Description.—Adult male: Crown clear gray; prominent white superciliary; line through eye black; underparts white, washed along sides with faint yellow; upperparts olive-green; wings unmarked; outer tail-feathers marked with white along the inner margin. Female: Similar, but crown tinged with greenish. Immature: Olive-green above, brightest on rump; dull yellowish below, brightest on the under tail-coverts. Length: 5 inches.
Range in Pennsylvania.—A migrant in May and September, apparently fairly regular and common in spring among the mountains, rare east of the mountains, but equally abundant everywhere in the fall.
The song of this bird is a series of chips, the tempo of which changes twice, the most rapid part of the song coming at the last. This bird is like a vireo in color but not in actions. Young birds are sometimes exceedingly common in the fall.
Tennessee Warbler
Parula Warbler