This rather yellowish green warbler, named for its least conspicuous character, forages lower than many species. It lays 4 to 5 eggs (March–May in west, June in east) in its nest on or near the ground. Polytypic. Length 5".
Adult male: dusky olive green upperparts, grayer on crown and nape. Whitish or yellowish narrow broken eye ring, indistinct dusky eye line. Greenish yellow underparts with indistinct blurry streaks. Undertail coverts always brighter yellow than belly. Adult female: duller and grayer than male. Immature: duller, similar to adult female.
Northern nominate is the dullest, West Coast lutescens is brightest yellow, Rocky Mountains and Great Basin orestera is intermediate, and coastal California sordida (mainly Channel Islands) is darkest green.
Compare with Tennessee warbler. In West,
