Lazuli Buntings are found over most of the United States and adjacent Canada west of the Great Plains in arid brushy areas in canyons, riparian thickets, chapparal, scrub oak, and open woodland. In summer in the western United States, they are common around thickets and streamside trees. In migration and in winter, they also occur in open grassy and weedy areas. The wintering range extends from southern Arizona and northern Mexico to southern Mexico.
The diet consists mostly of seeds and (especially in summer) insects (young are fed mostly insects). The nest is bult by the female in shrubs, vines, or low trees, typically around a meter above the ground. The female lays 3 to 5 (usually 4) eggs. At some nests, nestings are fed entirely by the female whereas at others the male assists. Young leave the nest around 10 to 12 days after hatching. If the female initiates a second clutch, males may feed the fledglings more. Fall migration begins early, with many birds already moving by late July. Migrants stray east of the breeding range on the Great Plains, especially i spring.
Lazuli Buntings (Passerina amoena) and Indigo Buntings (P. cyanea) are closely related sister species that hybridize where their breeding ranges overlap in the western Great Plains and eastern foothills of the Rocky Mountains of North America. Carling and Brumfield (2009) and Carling et al. (2010) undertook population genetic analyses to investigate the genetics underlying this interaction. Since the mid-20th century, Indigo Buntings have extended their breeding range into New Mexico and Arizona, but their interactions with Lazuli Buntings here have not been as extensively studied as in the Great Plains.Lazuli and Indigo Bunting males will defend territories against each other (behavior not typically seen between members of different species).
(AOU 1998; Kaufman 1996; Carling et al. 2010 and references therein)