ion; 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 CAERULEA. 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 ALAMAE. Rare summer resident;
in migration common.

759. =Dwarf hermit thrush.= HYLOCICHLA AONALASCHKAE. Rare migrant.

759a. =Audubon's hermit thrush.= HYLOCICHLA AONALASCHKAE AUDUBONI. Common
summer resident; breeds from 8,000 feet to timber-line.

759b. =Hermit thrush.= HYLOCICHLA AONALASCHKAE PALLASII. Rare migrant;
comes to the eastern edge of Colorado, just touching range of
_auduboni_.

761. =American robin.= MERULA MIGRATORIA. Summer resident, but not
common; some interesting questions arise in connection with intermediate
forms.

761a. =Western robin.= MERULA MIGRATORIA PROPINQUA. Abundant summer
resident; breeds from plains to timber-line.

765a. =Greenland wheatear.= SAXICOLA OENANTHE LEUCORHOA. European
species; a straggler taken at Boulder by Minot.

766. =Bluebird.= SIALIA SIALIS. Rare summer resident; west to base of
Rockies.

767a. =Chestnut-backed bluebird.= SIALIA MEXICANA BAIRDI. Summer
resident; not common; western form, coming east as far as Pueblo.

768. =Mountain bluebird.= SIALIA ARCTICA. Abundant summer resident;
breeds from plains to timber-line; in autumn roams up to at least 13,000
feet.

INDEX

Aerial song, 50, 51, 86, 87, 239, 268-270, 286, 287, 299-301.

Aiken, Charles E., xiii, 50, 63, 67, 118, 134, 136, 157, 161.

Arvada, 193, 194, 278, 289, 301.

Blackbird, Brewer's, 25, 98, 125, 126, 133, 139, 140, 141, 187, 215,
230, 259, 264, 266, 268, 271-274.
red-winged, 98, 142, 215, 271.
yellow-headed, 141, 142.

Bluebird, mountain, 22, 55, 67, 99, 128, 192, 231, 237, 259.

Bobolink, 286, 287, 289.

Boulder, 162, 178, 184, 186, 206, 279, 28