Many predators eat cardinals and their eggs and young. Falcons, hawks, owls, and other raptors can capture adults. Fledglings are often killed by domestic cats. Eggs and nestlings are commonly eaten by snakes, blue jays, and squirrels.
Cardinals and other birds that eat seeds and fruits play an important role in helping to disperse seeds, which can pass through the bird’s digestive system intact some distance from the parent plant.
To develop and maintain their bright color, cardinals need pigment chemicals called carotenoids in their diet. Indeed, nearly all red, pink, orange, and yellow birds — from tanagers and orioles to flamingos and goldfinches — must eat foods that contain this pigment, or else their feathers will look pale. These are the same pigments that color carrots, apricots, daffodils, egg yolks, and so on, and produce the oranges and yellows of fall leaves.
There are two other species in genus Cardinalis: the pyrrhuloxia (peer-oo-LOX-ee-ah), a grayish bird with red highlights, which lives in the desert Southwest, and the vermilion cardinal, which lives in Colombia and Venezuela. Considering the distribution of the three species, it's clear why ours is called the northern cardinal.