ANIMAL ECOLOGY OF JOHNSON COUNTY — 29 
in the case of the willow thicket, will bear a rough comparison 
with the wndergrowth stratum of the timber lands. An addi- 
tional stratum of decaying wood must also be taken into consid- 
eration if the hazel is occupying land that still bears evidence of 
former forest in the shape of stumps and other remains of once 
living trees. Hazel formations are represented on the township 
maps by interrupted heavy lines. 
(6) Thickets. Under the heading of thickets are taken into 
consideration such miscellaneous formations of young tree growth 
as have not yet reached sufficient size to be dignified by the 
name of forest. These usually contain a mixture of many species 
of woody plants, not infrequently hazel, young oak, young hick- 
ory, ash, etc., being present. They usually occur in small patches 
on the uplands, which are ordinarily occupied by oak. For the 
most part they represent an attempt of nature to reforest areas 
that have been denuded of their trees. This process has not yet 
reached that stage for the establishment of any one form as the 
predominating species. The abundance and variety of these 
plants make such thickets the home of many of our birds, in- 
cluding the vireos, thrushes, ete. This is also accomplished by 
the great abundance of insect life which is present. Here, too, 
we find the blue racer, attracted no doubt by the large number 
of bird nests with their eggs and fledglings, as well as the abun- 
dant insect life. With reference to life strata, these thickets 
yield to such analysis as that applied to the hazel. They are 
represented on the township maps by irregular tangles of wavy 
lines. 
(7) Cleared land with stumps still present. This is perhaps 
the most artificial of all the habitat classifications, inasmuch as 
it does not discriminate between the species of trees of which the 
stumps are the remains. It is taken into consideration because 
it provides an animal habitat differing from both the forest and 
the land after it has been put under cultivation. Its chief 
physical features different from the forest are a lack of shade 
and living trees and a decrease in humidity. Of the forest ani- 
mals, it retains only those which feed upon decaying wood or 
fungi. It therefore must be said to represent the soil stratum, 
the decaying wood stratum, and the forest fungus stratum of the 
