Swanson, David L., James L. Ingold, and George E. Wallace. 2008. “Ruby-crowned Kinglet (Regulus calendula). 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/ruckin doi: 10.2173/bna.119