[3] A 2008 phylogenetic study by Alström and colleagues confirmed that the members of this family form a clade quite separated from the Emberizidae, with affinities instead with the New World warblers (Parulidae), cardinals (Cardinalidae) or tanagers (Thraupidae), though their exact relationships are unclear.

[3] Timing with the cytochrome b DNA suggests that the Calcariidae diverged from a common ancestor around 4.2–6.2 million years ago, around the beginning of the Pliocene, possibly soon after spread of grasslands in North America as the climate in the late Miocene became drier and cooler.

Genetic analysis with cytochrome b DNA showed that the thick-billed longspur was most closely related to the two snow bunting species, and the three nested within the genus Calcarius.

[6] However, a 2007 study by Maley and Winker found substantial differences in the juvenile plumage between the two groups, supporting a species-level division.

[9][10] Additionally, the snow bunting has been recorded as a vagrant to Algeria and Morocco in North Africa, the Balkans, Greece and Turkey, and Malta.

McKay's bunting breeds solely on several islands in the Bering Sea, and winters primarily on the western coast of Alaska.

[14] Members of Calcariidae generally inhabit open areas, including prairies, plains, shores, farmland, and beaches.