621. =Northern shrike.= LANIUS BOREALIS. Common winter resident; on its return from the North in October it first appears above timber-line, then descends to the plains.
622a. =White-rumped shrike.= LANIUS LUDOVICIANUS EXCUBITORIDES. Common summer resident; breeds mostly on the plains; sometimes in mountains up to 9,500 feet.
624. =Red-eyed vireo.= VIREO OLIVACEUS. Rare summer resident; an eastern species, coming only to base of foothills; still, one was taken at 11,000 feet.
627. =Warbling vireo.= VIREO GILVUS. Common summer resident; breeds sparingly on the plains; commonly in mountains up to 10,000.
629a. =Cassin's vireo.= VIREO SOLITARIUS CASSINII. Rare or accidental summer visitor; not known to breed; a southwestern species.
629b. =Plumbeous vireo.= VIREO SOLITARIUS PLUMBEUS. Summer resident; common; breeds in foothills and mountains up to over 9,000 feet.
636. =Black and white warbler.= MNIOTILTA VARIA. Rare summer visitor; two records.
644. =Virginia's warbler.= HELMINTHOPHILA VIRGINIÆ. Common summer resident; western bird, but breeds along eastern base of foothills.
646. =Orange-crowned warbler.= HELMINTHOPHILA CELATA. Summer resident; not uncommon; common migrant; breeds from 6,000 to 9,000 feet.
646a. =Lutescent warbler.= HELMINTHOPHILA CELATA LUTESCENS. Summer resident; not uncommon: western form of the orange-crowned warbler; ranges to eastern base of mountains.
647. =Tennessee warbler.= HELMINTHOPHILA PEREGRINA. Rare migrant; eastern Colorado to base of mountains.
648. =Parula warbler.= COMPSOTHLYPIS AMERICANA. Rare summer resident; comes to base of foothills.
652. =Yellow warbler.= DENDROICA ÆSTIVA. Abundant summer resident; breeds up to 8,000 feet.
652a. =Sonora yellow warbler.= DENDROICA ÆSTIVA SONORANA. Summer resident; probably common; to the southwest _æstiva_ shades into _sonorana_.
654. =Black-throated blue warbler.= DENDROICA CÆRULESCENS. Rare migrant; one record.
655. =Myrtle warbler.= DENDROICA CORONATA. Common migrant; scarcely known west of the range.
656. =Audubon's warbler.= DENDROICA AUDUBONI. Abundant summer resident; breeds from 7,000 to 11,000 feet.
657. =Magnolia warbler.= DENDROICA MACULOSA. Rare migrant; breeds northward.
658. =Cerulean warbler.= DENDROICA RARA. Rare migrant; one record.