A cardinal's nest is a bulky structure of vines, leave and twigs. It is often hidden in a thicket. The nest is usually within ten feet of the ground. Three to four cardinal eggs will hatch after twelve days, and the fledglings leave the nest when they're between ten and twelve days old. Plant seeds and fruits comprise 90 percent of the cardinal's food in the fall and winter, and 40 to 50 percent of their food in the summer.