Ficken, Millicent S., Margaret A. McLaren, and Jack P. Hailman. 1996. “Boreal Chickadee (Poecile hudsonicus).” 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/borchi2 doi: 10.2173/bna.254