1915] 
Cahn: Ecology of Wingra Springs Region 
125 
physiographic features of the landscape are altered — the retreat 
of the pileated and ivory-billed woodpeckers with the destruc- 
tion of the forests, the vanishing of the shore birds with the 
draining of the swamp-lands, and the incoming of the birds 
of the open with the clearing of the land. 
Finally, it is the soil, acting with the preceding influences, 
though secondary and subordinate to them, which adds the 
next important factors to the list of species determinants. It 
is largely upon the nature of the soil (together*with the climatic 
conditions with which the soil is most closely associated) that 
the flora of a region is dependent, and the flora again exerts its 
influence over the fauna. Upon the plants, too, the birds are 
dependent for shelter, protection, and for nesting sites. 
In working out a problem in bird ecology, the investigator 
is carried into fields other than ornithological in the manner 
shown above, yet geology, climatology, geography, and botany 
are not the only foreign fields he must enter. When he under- 
takes a determination of the food of his subjects, the whole 
realm of invertebrate zoology must be faced, and as the food 
habits of a form are important, the subject is a whole may not 
be overlooked. And lastly mammalogy is encountered in con- 
nection with the enemies which the species must escape in order 
to maintain itself successfully. Thus it may be readily seen 
that the entire biota of a region must be surveyed in order 
to ascertain the position occupied by any form of animal life — 
the animal in its environment — and it is this environment 
that goes to form the almost endless chain which the animal 
ecologist must attempt to follow. 
Methods and Equipment 
In the present problem the methods of procedure and the 
equipment were as simple as possible. Field work was carried 
on regularly from October 5, 1913, to June 1, 1914, with the 
exception of the period from November 20 to February 1, when 
owing to illness, the investigation had to be given over. Data, 
however, covering this period were gathered the following 
winter (1914-1915), with approximately the same regularity 
observed during the first year, namely: four to six trips through 
the area a week, each trip occupying from four hours to the bet- 
