Distribution in the Americas
Orange-breasted Bunting is endemic to the Pacific slope in western and southwestern Mexico. It ranges from southern Nayarit south to western Chiapas, and along the Río Balsas drainage into western Puebla (Howell and Webb 1995). The elevational range extends from from sea level up to 1200 m above it, but Orange-breasted Bunting occurs below 900 m (Howell and Webb 1995, Vega Rivera et al. 2008).
Vega Rivera et al. (2008) modeled the potential distribution of Orange-breasted Bunting by analyzing its ecological niche. They found the bird in five of the six states they visited, including Jalisco, Colima, Michoacán, Guerrero, and Oaxaca, but not Nayarit. They found suitable habitat in around 40% of their study area and conclude that the bird has a more restricted distribution that shown in most field guides (Vega Rivera et al. 2008).
There is one prominent report of Orange-breasted Bunting outside of its normal range: a male was caught in a mist et near Mission, Texas, on 2 December 1972. Although this bird is actively traded, its captors believed it was a wild bird because it struggled when put in a cage and because it had brilliant and very well kept plumage (Novy and McGrew 1974).
Distribution outside the Americas
The Orange-breasted Bunting does not occur outside of the Americas. It is endemic to Mexico.
Orange-breasted Bunting inhabits dense but bushy arid to semi-arid thorn forest, brushy deciduous woodland, lowland scrub, edges, small short-grass or overgrown clearings, and roadsides (Edwards 1972, Binford 1989, Howell and Webb 1995, Parker et al. 1996). They occasionally are found in pine-oak forests when these border the habitats preferred by the bunting (Vega Rivera et al. 2008).
Vega Rivera et al. (2008) conclude that the bunting’s optimum habitat is tropical dry forest, which covered 32.2% of their modeled potential distribution (see below).
A study that modeled the Orange-breasted Bunting’s range surveyed 51 sites and noted the ecological factors that the bird seemed to prefer in order to map its potential distribution (Vega Rivera et al., 2008). Vega Rivera et al. (2008) determinted that seasonal precipitation, daily temperature fluctuations, and altitude are the main limiting factors in the distribution of Orange-breasted Bunting. The birds tended to favor areas that had highly seasonal precipitations and low daily temperature fluctuations. They were never found above 1200 m and usually occurred below 900 m, even though their habitat has an upper limit of around 1600 m (Vega Rivera et al. 2008). The birds also preferred little disturbed forest (48% of sightings) and a tree canopy covering of less than 40% (38% of point counts) over one of more than 70% (27% of counts). The study concluded that the Orange-breasted Bunting is not a generalist bird, but looks for specific ecological factors (Vega Rivera et al. 2008).
Census counts made in the Chamela-Cuixmala Biosphere Reserve, in Jalisco, compared migratory to resident species preferences for undisturbed, tall secondary, and short secondary forests (Hutto 1989). This study found that the Orange-breasted Bunting had a significant preference for the secondary habitats (Hutto 1989). This apparently contradicts the findings of Vega Rivera et al. (2008), because they conclude that the bird prefers little disturbed forest. However, Vega Rivera et al. (2008) mention that Hutto’s data, collected in February instead of the breeding season, may show a seasonal difference in the bunting’s habitat preference, which is further supported by changes in capture rates at their banding station in the same reserve. They conclude that Orange-breasted Bunting is likely a seasonal migrant, preferring forested areas in the breeding season, and congregating in grassy, secondary, or perturbed areas during the non-breeding season (Vega Rivera et al. 2008).
One fossil presumably belonging to an extinct member of Passerina has been discovered in Yepomera, western Chihuahua, Mexico (Steadman and McKitrick 1982). This site includes many waterbirds and one other species of passerine (a thrasher) from around 4 million years ago, in the Pliocene Epoch. Bone fragments identified as Passerina were intermediate in shape and size between P. amoena (Lazuli Bunting) and P. caerulea (Blue Grosbeak) (Steadman and McKitrick 1982).
These fossils were used to design a molecular clock with evolutionary rates of 1.6% and 2%. It found that the Passerina probably diverged from the Cyanocompsa between 4.1 and 7.3 million years ago, in the Late Miocene (Klicka et al. 2001).