There is very limited information on the reproduction of Orange-breasted Bunting. It breeds during the wet season (Vega Rivera et al. 2008), where birds reach breeding condition in mid to late May, and laying condition from mid to late June, although they are in breeding condition from late July to early August at higher elevations (Brewer 2011). The nest is a cup of grasses, roots, and dry leaves, lined with finer dry grasses and hidden low in a bush or thick shrub. It has a clutch of 3-4 eggs, bluish-white or greenish-white (Brewer 2011).
Soderberg (1956) states that while the bunting has been bred in captivity, when attempting to do so one usually has ‘to accept defeat with as good a grace as possible’.
An experiment in the Chamela-Cuixmala Biosphere Reserve in Jalisco, Mexico, included one Orange-breasted Bunting nest to determine the birds’ response to Brown-headed Cowbirds (Molothrus ater; Mendoza-Rodríguez et al. 2010). Of the 46 bird nests they found from July to September 2007, only one (of a Black-capped Gnatcatcher Polioptila nigriceps) was parasitized. The buntings did not respond to mounted cowbirds or attilas placed to find if the birds reacted differently to nest-parasites or ‘neutral’ birds (Mendoza-Rodríguez et al. 2010).