Indigo Bunting - Taxonomy

Taxonomy

The Indigo Bunting is included in the family Cardinalidae, which is made up of passerine birds found in North and South America, and is one of seven birds in the genus Passerina. It was originally described as Tanagra cyanea by Linnaeus in his 18th-century work, Systema Naturae. The current genus name, Passerina, is derived from the Latin term passer for true sparrows and similar small birds, while the species name, cyanea, is from the Latin word meaning dark or sea blue.

The Indigo Bunting is closely related to the Lazuli Bunting, and interbreeds with the latter species where their ranges overlap, in the Great Plains. They were declared to form a superspecies by the American Ornithologists' Union in 1983. However, according to sequencing of the mitochondrial cytochrome-b gene of members of the genus Passerina, it was determined that the Indigo Bunting and Lazuli Bunting are not, in fact, sister taxa. The Indigo Bunting is the sister of two sister groups, a “blue” (Lazuli Bunting and Blue Grosbeak) and a “painted” (Rosita's Bunting, Orange-breasted Bunting, Varied Bunting, and Painted Bunting) clade. This genetic study shows these species diverged between 4.1 and 7.3 million years ago. This timing, which is consistent with fossil evidence, coincides with a late-Miocene cooling, which caused the evolution of a variety of western grassland habitats. Evolving to reduce size may have allowed buntings to exploit grass seeds as a food source.