Blue jays are natural forest dwellers but are highly adaptable and intelligent. Their call "Jay! Jay!" is one of the sounds the bird uses and can do an excellent imitation of hawk calls. They are known to eat eggs or nestlings but they are mostly vegetarian eating acorns, nuts seeds and sometimes caterpillars, grasshoppers and beetles. Jays may store acorns in the ground and often forget where they put them.
Cardinals can be found year round in the eastern U.S. and due to their popularity are the state bird for several states. The male is very aggressive when he develops a territory and often will mistakenly attack his own reflection in windows. The male feeds the female during courtship and mates for life. They build their nests in shrubbery or heavily branched trees. The male Cardinal keeps it's red plumage all year long.
Both Cardinals and Blue jays like similar seeds as do several other birds:
Black oil sunflower seeds - attracts cardinals, woodpeckers, blue jays, goldfinches, purple finches and chickadees
Nyger - attracts goldfinches
Safflower seeds - attracts chickadees, titmice and downy woodpeckers
Suet - provides concentrated energy to help birds make it through freezing winter (woodpeckers love it).