August 1, 2018

Oaks—A Wildlife Powerhouse

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By Scott Meister

Whenever someone asks me, “How can I attract more wildlife to my backyard?” my response is always the same: “Plant an oak!”

Many homeowners avoid planting these stately trees because they think they’re slow-growing, but some oaks, such as the northern red oak, can grow more than 2 feet per year. More important than growth rate (especially if you’re a squirrel or woodpecker) is the value oaks hold for wildlife, which exceeds that of many species of trees.

Although nicknamed the Prairie State, Illinois was nearly 38 percent woodland prior to European settlement. Many of these areas were dominated by oaks, which kick-started wildlife’s centuries-long dependency on the trees for food and shelter.

Packed with fats and carbohydrates, acorns are an appealing source of much-needed nutrition (especially in fall and winter) for more than 100 species of wildlife, including white-tailed deer, turkeys, blue jays and squirrels. According to one study, wildlife can consume up to 83 percent of an oak’s acorn crop.

But not all acorns are created equal. Oaks belong to one of two groups, white or red. Acorns from swamp white, bur, post and other oaks in the white oak group contain less tannic acid than those from the red, making them more palatable—and preferable—to local wildlife.

Acorns clustered on a branch of an oak tree

Migrating songbirds are another guild that depends on oaks for food, although not for the acorns. More than 500 species of insects live and feed on oaks; other widely planted trees only support a handful. Because of this disparity, you’re more likely to attract migrating birds to your yard with oaks than, say, maples. Oaks’ catered bug buffets allow blue-winged warblers, American redstarts, common yellowthroats and other migrants to find food faster, saving time and energy for their long journeys ahead.

In addition to being a critical source of food, oak trees offer valuable shelter. Natural cavities can form in any tree, but larger species, oaks included, can support larger cavities without detriment to the trees themselves. This means more sizes and species of wildlife are able to claim squatter’s rights. Red-headed woodpeckers, identified as in greatest need of conservation by the Illinois Wildlife Action Plan, rely on cavities to raise their young as do eastern bluebirds and flying squirrels. Because they all readily nest in oaks, adding oaks to your yard can make all three great additions to your wildlife watchlist as well.

Even an oak tree’s leaves are superior when it comes to habitat. Leaves on deciduous trees “senesce” in fall, which means they die and dry up. On many trees the leaves soon drop, but the browning leaves on some oaks, including shingle oak, northern pin oak and black oak, remain on the branches through winter. This gives smaller animals cover from predators at a time when cover is scarce. When an oak does drop it leaves, they decay more slowly and remain in the environment longer than others, creating protected areas for mice, snakes, insects and other animals that shelter on the ground.

There’s a Greek proverb that states, “A society grows great when old men plant trees whose shade they know they shall never sit in.” Planting an oak tree in your backyard will not only enrich your quality of life today but also welcome and maintain healthy populations of wildlife for years to come.

Photo Credits

Photos by Forest Preserve District of DuPage County


Scott Meister is the Manager of Natural Resources with the Forest Preserve District of DuPage County.

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