They forage on the ground, in thickets, under story trees, and upper canopy trees. They consume many insect pests including moths, cutworms, grasshoppers, aphids, snails, and slugs. A great variety of weed seeds are also consumed. Cardinals are also very fond of wild fruits such as hackberries, dogwoods, hollies, mulberries, elderberries, sumac, and viburnums. The preferred foods for cardinals at bird feeders are sunflower seed, safflower seed, and white proso millet.
Courtship begins in late winter.
During the fall and early winter the male generally acts indifferent towards the female, and may act aggressively towards her when he comes into contact with her while foraging. However, at the beginning of the courtship season they can be seen peacefully foraging together. During this time the male can also be seen feeding the female bits of food. This behavior is known as mate-feeding. Mate-feeding is a large part of the cardinal's courtship.