LeSchack, Craig. R., S. Keith McKnight, and Gary R. Hepp. 1997. “Gadwall (Anas strepera).” 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/gadwal doi: 10.2173/bna.283