759b. =Hermit thrush.= HYLOCICHLA AONALASCHKÆ 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, 282. Breckenridge, 259, 293, 294, 302. Buena Vista, 32, 38, 112, 127, 132-136, 139, 146, 162, 193, 267. Bunting, lark, 187, 285-292. lazuli (also called finch), 25, 121, 154-159, 178, 187, 290. Burro ride, 223-256. Butterflies, 177, 252, 253, 266. Canary, 127. Cañon, Arkansas River, 43, 117. Cheyenne, 109, 170. Clear Creek, 184, 187, 197. Eagle River, 117, 125. Engleman's, 40. Grand River, 44, 125. South Platte, 206, 259, 278-282, 293. Catbird, 31, 36, 121, 133, 189. Chat, yellow-breasted, 186. long-tailed, 186. Chatterers, 302. Cheyenne Mountain, 91. Chewink, 36. Chickadee, black-capped, 66, 67, 76, 119. mountain, 66, 67, 73, 76, 77, 119, 212, 231, 235, 254, 262. Colorado Springs, 38, 42, 50, 68, 83, 89, 90, 117, 121, 155, 157, 160, 177, 178, 183, 187, 193, 210, 279. Cooke, Wells W., 24, 51, 67, 76, 134, 184, 261. Coot, American, 145, 146. Cottonwood Lake, 112, 146, 162. Coues, Dr. Elliott, 24, 76, 302, 303. Cowbird, 271. Coyote, 99, 100. Crane, 146. Crossbill, Mexican, 262, 263. Crow, 25. Denver, 26, 159, 177, 178, 179, 181, 183, 187, 193, 241, 263, 282, 289, 292. Dickcissel, 36. Dipper (_see_ water-ousel), 163-174, 209, 210. Dove, turtle, 43, 44, 97, 122, 126, 129, 186. Ducks, 72, 143, 146. ruddy, 143-145. East and West, birds of, compared, 19, 21, 23-27, 31-40, 43, 44, 54, 55, 62, 67, 69, 76, 90-95, 106, 119, 121, 125, 129-131, 133-136, 149-159, 186, 191-193, 198, 205, 215, 266, 270, 272, 286, 287. Flicker, red-shafted, 25, 55, 73, 119, 126, 213, 231, 254, 262, 298. yellow-shafted, 25, 55.