A very plain sparrow found in dense brushy woodlands and weedy fields. Gray overall with dull greenish back. Look for obvious dark stripes on head, usually brownish but darker in western Mexico. Sexes are alike; young birds are buffier and streakier. Fairly common but shy and sometimes difficult to see well. Always on or near the ground. Primarily a Mexican species, with limited range in U.S. and an isolated population in Costa Rica and Nicaragua. Listen for song, a series of sharp notes that speeds up towards the end. Compare with brighter Green-backed Sparrow of the Yucatan Peninsula; especially note different voice.