Forest Preserve District of Cook County, Illinois
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Food Chains in the Woodland
Nature Bulletin No. 602   April 30, 1960
Forest Preserve District of Cook County
Daniel Ryan, President
David H Thompson, Senior Naturalist

The main business of living things is to stay alive, grow and multiply. To do this each species, or at least some of its members, must find the right kind of food and enough of it. Feeding is so taken for granted and is so common-place that its importance is often overlooked.

Only green plants are able to live on raw sunlight, water and simple chemicals taken from the soil and the air. Hordes of animals, from very small kinds to very large ones, feed directly on plants. Other animals feed on these plant-eaters, thus getting their plant diet second hand. These, in turn, are preyed upon by large flesh-eaters -- one living upon the other -- and so it goes. This is a food chain. A great many of these food chains may start from a single plant such as a woodland tree. Furthermore, these food chains form an intricate web of interrelations between the eaters and the eaten which binds the forest community together.

To help understand how this system of checks and balances works, let us take as an example a single tree such as the Basswood, also called the Linden. This large tree with its characteristic ring of sprouts around the base is common in many of our forest preserves.

In spring the wingless females of a small moth lay clusters of eggs in crevices of the bark. These hatch into small green or gray cankerworms or inchworms which crawl up the tree and feed on the tender growing leaves, sometimes chewing most of the leaves on the basswood into ragged remnants. Dozens of migrating warblers and other insectivorous birds may be seen searching this tree for these small caterpillars. These little birds occasionally fall prey to hawks and owls, or their nests of eggs and young may be raided by squirrels which, again, may be caught unawares by a hunting fox. A large flesh- eating bird or mammal is usually considered to be the last link in these woodland food chains. However, after death by accident or from so- called "natural causes", the chain continues through the crows, opossums, fly maggots and carrion beetles which scavenge their carcasses. Finally, all of them contribute fertilizer to the soil that helps support our basswood tree. The food chain has gone full circle.

Many other chains, including many other insect chains, start from the leaves and buds. A man lost in the woods in winter can survive on a diet of the plump, reddish brown, rather tasteless buds. When food is scarce these also are eaten by squirrels and certain birds. Deer browse on the leaves, twigs and buds of the lower branches. In autumn after the leaves have fallen, bacteria, fungi and a wide variety of small animals begin the process of converting them into leaf mold. As they crumble, earthworms pull the fragments down into their burrows where they are eaten and the digested remains stirred into the soil.

The fragrant, creamy yellow clusters of flowers in early summer buzz with honeybees and bumble bees collecting nectar and pollen for their colonies Honeybee hives in hollow trees are often robbed by raccoons, while skunks devour bumble bee nests on the ground -- honey, young, adults and all. Our grandmothers dried basswood blossoms to make a tonic tea.

In 1973, the soil around our basswood will be peppered with holes when the 17-year cicadas burrow upward for their brief life aboveground. Since 1956 these young have been sucking juices from its roots. They leave their cast skins on the trunk, unfold their wings and set up a deafening din. Then for a few weeks every sort of woodland flesh-eater will gorge on cicada meat.

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