124 Bulletin Wisconsin Natural History Society [Vol. 13, No. 3 
IX. Ecological Discussion of the Bird by Species 151 
X. Summary and Conclusions 172 
XI. Bibliography 173 
XII. List of the Species of Animals Identified 174 
I. INTRODUCTION 
Relatively little work has been done thus far on the ecology 
of vertebrates, abundant as they are in practically every un- 
disturbed locality. The abundance of such animals in the 
vicinity of Madison, Wisconsin, was the incentive which lead 
to the ecological investigation the results of which are to be set 
forth in the following pages. 
The problem was undertaken with especial reference to birds, 
but as no ecological problem can well be confined to a single 
animal or even to one group of animals, the writer very quickly 
found himself dealing not only with birds, but with vertebrates 
in general, a large number of invertebrate species, as well as 
with the botany of the region selected. All of these must be 
considered in some detail if one would come to any conclusions 
as to the relation of birds to their environment; one factor de- 
pends on another as does one species upon another, thus making 
a sort of endless chain. The bird life of any region — the exist- 
ing life of whatever form for that matter — is closely linked with, 
though perhaps not dependent upon such great general factors 
as the climatic, physiographic, and soil conditions found in the 
region under consideration. A moment’s reflection will show, 
no doubt, the very great influence these factors must have on 
the avifauna, for it is such influences as temperature, humidity 
and light (the chief climatic factors) that function in a large 
manner as the determiners of species that may exist and thrive 
in any particular locality. The physiographic features of the 
country are perhaps of the most importance in determining 
the species in a given formation, as the presence or absence of 
hills, valleys, rivers, lakes, woods, or open fields will limit and, 
define the forms of life that may thrive therein. Every species 
of animal and plant life is adapted to some particular mode of 
life, to some one habitat above all others, and it is there that 
this species is found at its optimum. The fact that species 
persist and thrive in some one habitat better than in another 
is proof of this, as is also the disappearance of species as the 
