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
FOOD CHAINS IN THE WOODLAND
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
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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Update: June 2012