Forest Preserve District of Cook County, Illinois
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Hollow Trees
Nature Bulletin No. 335-A   March 3, 1969
Forest Preserve District of Cook County
Roland F. Eisenbeis, Supt. of Conservation
George W. Dunne, President

HOLLOW TREES
You may have heard the expression: "They couldn't see the forest for the trees". There was a time, especially in Germany, when foresters grew trees as farmers grow cabbages: thousands of acres covered with just one kind planted in long rows that were kept free of all seedlings, underbrush, dead or injured trees and everything but perfect specimens. For a while these plantations produced astonishing yields of lumber and the Germans boasted of them as models of "efficiency". The fact that they supported practically no wildlife -- only a few birds, no food for deer, and so forth -- was contemptuously dismissed.

Suddenly the soil turned "sick". Insect pests swept through them like forest fires. They withered and died. Finally the Germans turned to the planting of mixed forests, including "worthless" species such as beech and birch, where natural reproduction and undergrowth was permitted. They put up nesting boxes to attract the many kinds of birds that help control harmful insects. They actually imported and propagated some species, including owls. They planted earthworms in the soil. They found that woodlands which comprise a natural community of a great variety of living things was more productive and gave less trouble than artificial plantings. They became apostles of the Naturschutz -- a natural forest. We now know that wildlife is valuable for more than meat and fur, or to provide sport for the hunter, or as something sacred to the long-haired few who write sentimental essays and poems about "naytchah".

Some of the most useful, valuable and interesting animals of our American woodlands are missing when there are no trees with dead limbs or hollow trunks. Honey bees and other bees, wasps, the hibernating butterflies, moths, certain mosquitoes, spiders, snails, tree frog, and many other kinds of insects, lower animals and fungi are found in such places. A list of some of the higher animals that nest, den or find shelter there, and perhaps food, includes: raccoon, possum, deer mouse, all the tree squirrels, all the woodpeckers, chickadee, tufted titmouse, the nuthatches, brown creeper, bluebird, three kinds of wren, crested flycatcher, prothonotary warbler, chimney swift, purple martin, tree swallow, starling, house sparrow, screech owl, barn owl, barred owl, sparrow hawk, and eight kinds of ducks -- wood duck, bufflehead, American goldeneye, Barrow's goldeneye, fulvous and black-bellied tree ducks, hooded merganser and American merganser.

A good way to learn what lives in such trees is by sauntering through the woods in winter. Squirrels prefer the holes made when a small limb is broken off and decays back into the trunk. Woodpeckers drill holes in dead limbs and excavate a nest cavity which is frequently used the next year by other kinds of birds. One day we spied some chunks of honey comb at the foot of a tall red oak in the woods back of Punkin Knob. Deer mice are fond of honey and sometimes rob a hive in midwinter. Sure enough, on the next balmy sunny day there were bees streaming in and out of a hole up on the trunk of that tree. Not far from there is a hollow linden where possums and a family of flying squirrels have their dens. Farther on, there is a big soft maple on the bank of a small creek. Leading to it, in the snow, we have seen raccoon tracks and on the bark, their claw marks and a few hairs. That must be the varmint that scared our "missus" half to death when he stuck his head up and out of the garbage barrel.

Learn to saunter. Natura non facit saltum.


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