Very local but fairly common in highland marshes of central Mexico; endemic. Favors extensive reed beds bordering lakes and adjacent bushes near water. Male is distinctive, with black mask blending into dark greenish upperparts (lacks pale border to mask of Common Yellowthroat, which occurs in same areas); also note extensively yellow underparts and dark legs. Female is darker overall than female Common Yellowthroat, with dark (not pinkish) legs. Voice subtly distinctive.