Lowther, Peter E., and James L. Ingold. 2011. “Blue Grosbeak (Passerina caerulea).” The Birds of North America, edited by Paul G. Rodewald. Ithaca: Cornell Lab of Ornithology. Retrieved from the Birds of North America: https://birdsna.org/Species-Account/bna/species/blugrb1 doi: 10.2173/bna.79