Despite the Varied Bunting's widespread distribution in central Mexico, its conspicuous behavior, and its striking male plumage (a 1901 painting by Louis Agassiz Fuertes is used as a frontispiece for Coues 1903), little information is published about the life history of this species. Species accounts are anecdotal, and distributional and other information is mostly historical (e.g., Baird et al. 1874b, Ridgway 1901, Van Rossem 1931c, Brandt Brandt 1940, Brandt 1951). There is almost no published information on the natural history of the Varied Bunting in Baja California and its center of distribution, mainland Mexico. To provide information for this account, KDG studied Varied Buntings at Chino, Rock Corral, and Montosa Canyons in southeastern Arizona in August 1992 and May–September 1993–1995. She banded and color-marked 33 adults and 8 nestlings, observed behavior, found nests, and recorded vocalizations. CWT examined egg collections and museum specimens to gain new insight on egg and plumage characteristics.
Varied Buntings occur from the southern borders of Texas, New Mexico, and Arizona, through Mexico, including Baja California, to Guatemala. They occupy habitat characterized by arid thorn brush at riparian edges, thorn forest, scrubby woodland, and overgrown clearings, and are absent from human residential areas.
Varied Buntings share the same sequence of molts and plumages as other Passerina species, and first-year males exhibit delayed plumage maturation. Songs are similar to those of Indigo (P. cyanea) and Lazuli (P. amoena) buntings in that individuals share syllables, neighboring males share songs, and population repertoire is limited.
Varied Buntings, however, have larger syllable repertoires, their songs are not stereotyped, and their singing activity depends on rainfall.
Breeding in the Varied Bunting also depends on rainfall. In Arizona, when summer rains are delayed, nesting may not begin until August. Eggs are polymorphic in color among populations, a rare phenomenon in passerine birds.