Jones, Stephanie L., and John E. Cornely. 2002. “Vesper Sparrow (Pooecetes gramineus).” 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/vesspa doi: 10.2173/bna.624