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 May, 1914 BIRDS O1 NORTHERN ,MONTANA 141 1.911 (CovoR, my, 1912, p. 30), but I now believe that the birds seen by me in Gallatin County in May (AVE, xxvm, 1911, p. 46), also belong to this subspecies. Vireosylva olivacea. Red-eyed Vireo. Summer resident in the prairie region, nesting in cottonwood groves. Rare north of the Sun River and not very common there. Vireoylva gilva swainsoni. Western Warbling Vireo. Common summer resident in aspen groves in the mountains up to about 5500 feet. Most abun- dant along the foothills. Found all summer in cottonwoods in the prairies, but in small numbers. Lanivireo solitarius cassini. Cassin Vireo. Observed on the West Fork of the Sun River, at an altitude of about 5500 feet, on September 3, 1912. Vermivora celata elata. Orange-crowned Warbler. Common summer Fig. 47. NEST AND EGOS OP McCowN LONGSPUR, resident of aspen groves in the mountains from the lower foothills to about 6000 feet. Dendroica aestiva aestiva. Yellow Warbler. Abundant summer resident of cottonwood groves and willow thickets in the prairie region. Migration dates: May 22, 1912, August 18, 1911. Nesting begins early in Jnne and young are on the wing about the first week in July. Dendroica auduboni auduboni. Audubon Warbler. Common summer resident of evergreen forests in the mountains, occuring throughout the Can- adian zone. Dendroica striata. Blackpoll Warbler. Common migrant in cottonwood groves in the prairie region. Observed near Choteau in considerable numbers May 22 to 25, 1912. This region is probably at about the western limit of the migration range of this species in Montana.