Blue jays mainly eat nuts, corn, grains and seeds. They also eat various types of insects and have been occasionally known to raid the nests of other birds to feed on nestlings and eggs.
Among the nuts and seeds that blue jays eat are acorns, peanuts, weed seeds and beech mast. They grasp nuts firmly in their feet and peck them open with their powerful beaks. Their penchant for acorns causes blue jays to scatter them, thereby aiding the spread of oak forests. On the ground and in shrubs and trees, blue jays feed on caterpillars, grasshoppers and beetles. They also eat flying insects from the air. Sometimes they store food in caches and eat it later. They have been known to feed on injured or dead mammals and birds.
Blue jays avidly eat sunflower seeds, peanuts and suet from tray feeders. However, they are often intimidated by other species such as gray squirrels, woodpeckers, grackles and scrub-jays when they visit feeders. Sometimes blue jays imitate the calls of hawks and other raptors, possibly to frighten other bird species away from food. They also use similar calls to warn other blue jays when predators are near and are sometimes bold enough to chase owls and hawks away.