721b. =Western house wren.= TROGLODYTES AËDON AZTECUS. Common summer resident; from plains to 10,000 feet; raises two broods, sometimes three. 722. =Winter wren.= ANORTHURA HIEMALIS. Rare resident; no nest found. 725a. =Tulé wren.= CISTOTHORUS PALUDICOLA. Summer resident; not uncommon; breeds from plains to 8,000 feet; some remain all winter in hot-water swamps. 725c. =Western marsh wren.= CISTOTHORUS PALUSTRIS PLESIUS. Summer resident; not uncommon locally. 726b. =Rocky Mountain creeper.= CERTHIA FAMILIARIS MONTANA. Common resident; in breeding season confined to the immediate vicinity of timber-line, where some remain the year round. 727. =White-breasted nuthatch.= SITTA CAROLINENSIS. Resident; not common. 727a. =Slender-billed nuthatch.= SITTA CAROLINENSIS ACULEATA. Common resident; western form; commonly breeds from 7,500 feet to timber-line. 728. =Red-breasted nuthatch.= SITTA CANADENSIS. Not uncommon resident; migrant on the plains; resident in the mountains to about 8,000 feet, sometimes 10,000. 730. =Pigmy nuthatch.= SITTA PYGMÆA. Abundant resident; mountain bird; makes scarcely any migration; most common from 7,000 to 10,000 feet. 733a. =Gray titmouse.= PARUS INORNATUS GRISEUS. Resident; not common; southern species, coming to eastern foothills. 735a. =Long-tailed chickadee.= PARUS ATRICAPILLUS SEPTENTRIONALIS. Not uncommon resident; winters on plains and in foothills; breeds from 7,000 to 10,000 feet; sometimes on plains. 738. =Mountain chickadee.= PARUS GAMBELI. Abundant resident; nests from 8,000 feet to timber-line; ranges in the fall to the tops of the loftiest peaks. 744. =Lead-colored bush-tit.= PSALTRIPARUS PLUMBEUS. Resident; not common; western species, coming to eastern foothills. 748. =Golden-crowned kinglet.= REGULUS SATRAPA. Rare summer resident; rather common in migration; breeds only near timber-line at about 11,000. 749. =Ruby-crowned kinglet.= REGULUS CALENDULA. Abundant summer resident; breeds from 9,000 feet to timber-line. 751. =Blue-gray gnatcatcher.= POLIOPTILA CÆRULEA. Rare summer resident; breeds on the plains and in the foothills. 754. =Townsend's solitaire.= MYADESTES TOWNSENDII. Common resident; breeds from 8,000 to 12,000 feet; winters in mountains, though stragglers are sometimes seen on the plains. The author saw a pair on plains near Arvada, in company with a young, well-fledged bird. 756a. =Willow thrush.= HYLOCICHLA FUSCESCENS SALICICOLA. Summer resident; rather common; breeds in foothills and parks up to about 8,000 feet. 758a. =Olive-backed thrush.= HYLOCICHLA USTULATA SWAINSONII. Rare migrant. 758c. =Alma's thrush.= HYLOCICHLA USTULATA ALAMÆ. Rare summer resident; in migration common. 759. =Dwarf hermit thrush.= HYLOCICHLA AONALASCHKÆ. Rare migrant. 759a. =Audubon's hermit thrush.= HYLOCICHLA AONALASCHKÆ AUDUBONI. Common summer resident; breeds from 8,000 feet to timber-line.