Northern Cardinal Overview, All About Birds, Cornell Lab of Ornithology
Indiana's State Bird: The Northern Cardinal - WonderLab
Annual Great Backyard Bird Count
All About Birds California Princeton University Press
Male Northern Cardinal in the Snow - FeederWatch
Cornell Lab of Ornithology—Home Birds, Cornell Lab of Ornithology
For Male Cardinals, the Redder the Better
Northern Cardinal Overview, All About Birds, Cornell Lab of Ornithology
SIB “Bird of the Week” – Northern Cardinal – SIB
All About Birds Southeast Princeton University Press
Cornell Lab of Ornithology—Home Birds, Cornell Lab of Ornithology
A Rare Bird Indeed: A Cardinal That's Half Male, Half Female - The New York Times
A veteran bird-watcher gives Merlin bird ID app a test drive