Range.--Interior of North America, breeding from Manitoba and mountains of New Mexico to Alaska; winters in Gulf States and southward; rare in Atlantic states north of South Carolina.
=646a. Lutescent Warbler= (_H. c. lutescens_). Similar to No. 646, but greener above, yellower below; underparts distinctly yellow with a dusky wash.
Range.--Pacific coast; breeding in mountains from southern California to Kenai Peninsula, Alaska; winters from California south into Mexico; east to Colorado in migrations.
=646b. Dusky Warbler= (_H. c. sordida_). Similar to No. 646a, but decidedly darker, bill and feet larger, wing shorter and tail longer. (Ridgw.)
Range.--Breeds in Santa Barbara Islands, California; later occurs on adjoining mainland.
=472. Beardless Flycatcher= (_Ornithion imberbe_). L. 4.5; W. 2.10. _Ads._ Bill small, narrow, upper mandible decidedly curved; above gray tinged with olive, below grayish white with a yellow tinge.
Range.--Central America; north in spring to Lower Rio Grande Texas.
=472a. Ridgway Flycatcher= (_O. i. ridgwayi_). Similar to No. 472, but larger, W. 2.2; grayer, little if any sulphur tinge on underparts. (Ridgw.) _Notes._ Call, a shrill _piér_ repeated; song, from the tree-tops, _yoop_, _yoop_, _yoopeédeedledee_. (Stephens.)
Range.--Southern border of Mexican tableland north in spring to southern Arizona.
=616. Bank Swallow= (_Riparia riparia_). L. 5.2. _Ads._ Below white, a broad grayish brown band across the breast; above grayish brown. _Yng._ Similar, but brown areas more or less tipped with rusty.
Range.--Northern hemisphere: in America, breeds from northern New Jersey, Kansas, and southern California, north to Labrador, and Alaska; winters south to Brazil.
=617. Rough-winged Swallow= (_Stelgidopteryx serripennis_). L. 5.5. _Ads._ Above grayish brown; below grayish white, whiter on belly; barbs on outer vane of outer primary recurved. _Yng._ Plumage more or less tipped with rusty.
Range.--United States; breeds from Mexico north to Massachusetts, Manitoba, and British Columbia; winters in Central America.
=623. Black-whiskered Vireo= (_Vireo calidris barbatulus_). L. 6. _Ads._ _A dusky streak on either side of the throat_, crown slate _without_ a black border; back olive-green; below white, lower belly, under tail-and under wing-coverts yellowish; no wing-bars. _Notes._ Resemble those of No. 624 but song more emphatic and hesitating.