by Kathy Heidel, Senior Interpretive Naturalist
Suburban Hennepin Regional Park District

"No other tree provides as much for as many as does the Oak" - D.W. Stokes

Plants produce seeds to ensure the future of their species. Overproduction is common, so
what happens to all the extra seeds? They're eaten, that's what. The "wildlings" get them!

Let's see how the mighty oak trees affect the wild world.

Mother White, Bur or Red Oak drops her acorns in late August and early September. But even before the seeds are ripe enough to fall, wild creatures are gathering them. Flocks of bluejays, grackles and blackbirds pluck the green acorns from the branches and consume them on the spot or store them for later meals. Squirrels and chipmunks scramble up into the oak's canopy and chew off the branch tips.

The leafy stems, with new acorns attached, fall to the ground. A squirrelly free-for-all ensues with the chipmunks getting a large share of the harvest. One "chippie" can haul away four or five acorns at a time.

White and bur oak acorns sprout right after hitting the ground. Nutrients are rapidly transferred from the nuts into the new seedlings. Gray squirrels bite off the pointed acorn tips, which prevents sprouting and loss of food value. The acorn therefore keeps better as a future food source.

Other "wildlings" that relish acorns are black bears, raccoons, wild turkeys, grouse, pheasants, white-footed mice, deer and ducks. White and bur oak acorns, which are sweeter and thus consumed first, consist of about six percent proteins and sixty-five percent carbohydrates. Red oak acorns have a higher fat and tannin content. Tannins are bitter tasting chemicals that can interfere with digestion. Since all oaks contain tannins in their leaves and acorns, those with higher amounts of tannin are less attractive to herbivores. Squirrels bury red oak acorns in the forest floor where rain and snow gradually lessen the tannin content over winter. In spring the nuts are fit to eat and also able to sprout.

For some animals acorns are the "staff of life." Wood ducks forage heavily on white oak acorns before beginning their fall migration. Deer also favor the nutritious nuts. Acorns are quickly converted to energy-producing fat for both animal species. Recent heavy acorn crops coupled with mild winters have led to an increase in local wild turkey populations. Like the Passenger Pigeon, turkeys are mast (nuts) feeders. Early explorers in America told of huge flocks of passenger pigeons that stripped oak trees of nuts in a matter of minutes.

By the end of the 1800s the cutting of forests to make way for farmers had so reduced the mast supply that turkey and pigeon populations plummeted. Market hunting decimated the flocks of birds even more. By 1912 the passenger pigeon was extinct and turkeys were nearly so. In addition to the "wildlings" depending on acorns, numerous tribes of Native Americans used acorns as a food staple. Bread served at the first Thanksgiving was likely made from acorn flour.

Acorns are of value beyond being food sources. An insect called the Acorn Weevil lays eggs inside ripe acorns where the wormy offspring consume their nutty meals in safety. Woodpeckers gather the acorns and consume both nutmeats and juicy worms! Uneaten worms eventually exit as beetles from a hollow acorn. When the young beetles exit, the empty acorn shell is a waiting apartment for spiders, millipedes, or the eggs of the Acorn Moth. Eventually the acorn is decomposed by fungi and reverts to soil. Many seeds that survive the "wildlings'" banquets sprout and grow into new trees.

The bark fissures of a mature oak tree often hide tiny insects, spiders, insect larvae, and the stored seed-meals of nuthatches and woodpeckers. Young spiders use the catkin-like oak flowers as niches, where they trap small insect meals.

In May returning Blue-gray Gnatcatchers and hummingbirds gather the dry web-covered flowers to use in nest construction. Warblers and other insect-eating birds glean the tender leaves for camouflaged caterpillars and the grown spiders.

Native leaf-eating insects rarely kill off the oak trees. An infestation of tent caterpillars or gypsy moth larvae may defoliate the tree, but the tree reacts by "loading" its remaining and newly sprouted leaves with phenol compounds. The phenols stunt caterpillar growth and reproduction. "Wildlings" attracted to these larval feasts are cuckoos, pewees, wrens, vireos, orioles, and many other bird species. Predatory insects such as assassin bugs, caterpillar hunters and mantises prey on the leaf-eating worms, too.

Oak leaves, despite being tannin-rich, host many other life forms: leaf miners, (50 or more species), June beetles, gall wasps, walkingsticks, cicadas, butterflies, moths, fungi, lichens, lace bugs and oak borer beetles are examples. Large oaks provide support for squirrel dreys and hawk and owl nests; sleeping platforms for squirrels, gray foxes and nighthawks; den cavities for woodpeckers as well as bears and raccoons.

Blankets of oak leaves collect on the ground each fall. Slow to decompose, they insulate seeds and seedlings of numerous wildflowers, shrubs, and trees from winter's dryness and cold. These same leaves protect frogs, worms, insects and arthropods from freezing to death.

Though an oak tree may live for 600 years, it eventually dies and falls to the earth. The slowly rotting branches and trunk get spongy and soft enough for ground beetles, blue-spotted salamanders, bald-faced hornet queens, centipedes, and ants to burrow in and find cozy, dark, safe homes. Decomposers such as fungi, mites, springtails, millipedes, worms and bacteria hasten the breakdown of the mighty tree. Finally, when the last vestiges of reddish wood dust are obscured, then grasses, flowers and seeds begin the cycle again.

You can help Three Rivers Park District convert old farmland to oak groves by contributing to Forests Forever (phone 763/559-9000).

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