As with most oaks, the nuts of this species are eaten by many birds and mammals. Acorns are a large component of the hard mast (nuts) that fall to the ground in autumn, providing winter food for deer, squirrels, bear, mice, ducks, grouse, quail, turkey, blue jays, nuthatches, woodpeckers, and more.
The larvae of acorn weevils eat acorns, too! If you collect acorns, don't be surprised if a few contain these grubs. Once the larvae exit the acorn, they burrow into the ground to become skinny-nosed, brown beetles.
Bur oak sustains many other types of insects, providing both food and habitat. Butterfly caterpillars that feed on the leaves include the red-banded, northern, white-M, striped, and banded hairstreaks. Skipper larvae that eat bur oak include the sleepy and Juvenal's duskywings. Hundreds of moth species use oaks as their larval food plants, and so do longhorned beetles, whose larvae are borers in the wood or bark. Treehoppers, leaf beetles, lacebugs, walkingsticks, and many other insects feed on the leaves.
The many leaf-eating insects on oaks are eaten by a variety of invertebrate predators that hunt them on the leaves, branches, and bark. Crab spiders and ambush bugs stalk the surfaces of the tree. Orbweaver and other web-building spiders use tree branches as the foundations of their nets for capturing flying insects. Robber flies zip around the spaces among the leaves and branches hunting just about any invertebrates they can capture.
The many insects that live on and around oaks provide nourishment for dozens of species of insect-eating birds. Many songbirds, even those that are otherwise seed- or fruit-eaters, must eat insects during breeding season to have the extra protein in order to reproduce successfully and feed their growing nestlings.
The bitter tannins (chemicals) that oak leaves contain are the tree's defense against leaf-eating animals. Many insects have digestive systems that can overcome the bitter chemicals, but many mammals prefer to eat other leaves.
The extinct passenger pigeon, a species that used to feed in flocks of thousands of individuals, fed heavily on acorns.