ルリノジコ Passerina cyanea

Breeding males are entirely blue with a slightly darker head. Females are plain brown with a whitish throat, bluish tail, and faint streaks on the underparts. Breeds in shrubby areas at the edge of forests and fields. Males often sing from a high exposed perch. Winters mainly in Middle America and the Caribbean, where it frequently gathers in flocks in weedy fields. Females can be very difficult to distinguish from Lazuli Bunting, although their range doesn't overlap much. Indigo usually shows more streaking on the underparts; also note fainter wingbars, duller breast, and more contrasting whitish throat.