I also think this is Yellow-breasted Bunting. Compared to Chestnut Bunting, there seems not to be enough chestnut in the uppertail, the head pattern seems wrong (poorly-marked malr, as Gary noted, but well-marked surround to ear coverts and sides of crown), and the breast seems a rather clean yellow (female Chestnut usually shows traces of the males breast pattern). Also, the median/lesser coverts show clear white fringes (again, a reflection of the male plumage) and the primary projection is very short (barely extending beyond the tertials - compare to the Chestnut posted by Geoff). Structurally I think this bird has the chunky, 'bull-necked' appearance typical of Yellow-breasted.
