Medium-sized warbler, 11 to 14 cm. Upperparts plain dusky olive-green, brighter yellow on rump and upper-tail coverts, grayer on crown and hind-neck. Crown with brown-orange patch, usually concealed. Eyes black, eyelids white or yellow, separated by dusky eye-line. Underparts greenish-yellow, faintly streaked. No wing bars. Bill narrowly wedge-shaped, very acute at tip. Sexes similar in color and pattern, but females tend to be duller with less distinct or absent crown-patch (Sogge, Gilbert, and Van Riper III 1994).
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 Bozeman area, normal migration periods are May 10 to 25 and late August to September 20.
Prefers habitats with shrubs and low vegetation, often in aspen forest or in riparian or chaparral areas which provide cover for its nest (Sogge, Gilbert and Van Riper III 1994).
Gleans insects from leaves, blossoms, and the tips of boughs, but also eats some berries and fruit and is attracted to suet feeders in the winter (Sogge, Gilbert and Van Riper III 1994).
Nesting is from early Jun to mid- August. Nests well concealed, often on or near ground or in small crevices or depression in ground/rock, along shady hillside, on slopes or steep banks, sheltered by overhanging vegetation. Also found in shrubby bushes, ferns, vines. Nest is a small open cup. Eggs are short, ovate, white or creamy in color with reddish-brown or chestnut speckling. Clutch size typically 4 to 5 eggs.