Smith, Kimberly G., Sara Ress Wittenberg, R. Bruce MacWhirter, and Keith L. Bildstein. 2011. “Northern Harrier (Circus cyaneus).” 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/norhar doi: 10.2173/bna.210