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.