Cardinals mate for life and are primarily monogamous. After the male has chosen a female, the two begin to build a nest using leaves, grasses, bark and small twigs that they gather and weave together. The nest is usually lined with animal hair and soft grass.
Female cardinals lay three or four eggs and then incubate them for 12 to 13 days. The male occasionally helps with incubation. Once the eggs hatch, the baby cardinal hatchlings eat as often as eight times per hour, generally feasting on insects. Baby cardinals grow rapidly; they are nearly the size of their parents by day eight and are flying by day 10.