Comments: Composed of two groups: ERYTHROGASTER (Barn Swallow) breeding in North America and RUSTICA (European Swallow) breeding in Eurasia (AOU 1998). Zink et al. (1995) found that populations on Asian and North American sides of Beringia exhibited a level of mtDNA differentiation intermediate between populations and species; however, sample sizes were small and no formal taxonomic change was recommended. See Sheldon and Winkler (1993) for information on intergeneric phylogenetic relationships of Hirundininae based on DNA-DNA hybridization. May form a superspecies with H. LUCIDA, H. AETHIOPICA, H. ANGOLENSIS, H. ALBIGULARIS, H. DUMICOLA, H. TAHITICA, and H. NEOXENA (AOU 1998).