A 15-cm-long bird with a sturdy, slightly hooked bill, blue-gray crown, white eyebrow (bordered above and below with black), dark olive back, darker wings and tail, pale, unstreaked underparts, and a red eye (brown in fall juveniles); immatures and some fall adults are yellow on the flanks and undertail coverts; subspecies flavoviridis
, which sometimes occurs in California and Texas, is yellower overall, with less distinct black lines on the head.
For a comprehensive review of the conservation status, habitat use, and ecology of this and other Montana bird species, please see Marks et al. 2016, Birds of Montana.
Western Hemisphere Range
In the Bozeman area, normal migration periods are May 23 to June 10 and August 20 to September 10.
More often heard than seen. Range wide, breeds in deciduous and mixed deciduous-coniferous forest. Absent from sites where understory shrubs are sparse or lacking. Often found near small openings in forest canopy. Can occur in residential areas, city parks, and cemeteries where large trees grow. During spring and fall migration uses a greater variety of forested habitats than during breeding season, but still prefers deciduous woodland over conifers. Winter range finds them present in various forested habitats from sea level up to 3000 m elevation (Cimprich et al. 2000).
In North America, consumes mostly insects, particularly caterpillars. During breeding season most often observed foraging in canopy vegetation. Also eats various small fruits, most frequently in late summer and fall. In winter, mostly frugivorous (Cimprich et al. 2000).
Nest is built in terminal or sub-terminal fork of branch in live midstory to understory tree or shrub, frequently shaded and concealed by vegetation above. Eggs are oval to short oval. They are dull white speckled irregularly and sparsely. Clutch size ranges from 1 to 5 eggs (Cimprich et al. 2000). Near Fortine, egg dates range from June 29 to July 8; most young leave the nest in early July. Statewide, Red-eyed Vireos breed from mid-June through July.