Northern Cardinal - American Bird Conservancy

Northern Cardinal: Overview & Identification

The Northern Cardinal: A Familiar and Recognizable Bird in North America – Nature Blog Network

U.S. Fish and Wildlife Service - Pyrrhuloxia are the northern cardinals' desert cousins. This male pyrrhuloxia looks a bit like a female cardinal, but he has a yellow bill to distinguish him

Speaking of Nature: A winter classic: the northern cardinal

Northern Cardinal (Cardinalis cardinalis)

Northern Cardinal : Minnesota Breeding Bird Atlas

Northern Cardinal Audubon Field Guide

Northern Cardinal - American Bird Conservancy

Northern Cardinal - eBird

Northern Cardinal Overview, All About Birds, Cornell Lab of Ornithology

Northern Cardinal - American Bird Conservancy