1915] 
Cahn: Ecology of Wingra Springs Region 
135 
V. INFLUENCE OF TOPOGRAPHIC FEATURES ON BIRD LIFE 
Before passing on, it may be well to point out more specifi- 
cally the influence of the topographic features on the bird life. 
These features lend themselves to a division into biotic associa- 
tions, which it will be well to outline at this point. 
The Limnetic , or Lake Association 
This association comprises only the lake to the shore line, but 
does not include the latter. It is characterized by the various 
species of fish found throughout its extent, the most common 
of which are the bluegill, silver-bass, sun-fish, and carp. These 
at least are not to be found in the springs. The reptiles are 
represented by the painted turtle and the snapping turtle; 
the former is to be found quite often in the swamp, while the 
latter is more strictly limnetic, yet both may be said to be char- 
acteristically aquatic. There are no amphibians that can lay 
claim to being typical of this association: all of the amphibians 
of the region have been found along the lakeshore, but infre- 
quently when compared with their abundance in some other 
association. 
The birds of this association are, of course, aquatic, and are 
represented by such species as the grebes, coot, and many of 
the ducks, notably the bluebills, bufflehead, golden-eye, ruddy, 
canvas-back, and redhead, together with the loon and the 
cormorant, the latter being a rare visitor to the formation. 
The Limniotic, or Swamp Association 
This is the most important of the associations both in extent 
and in the number of species of animals represented. The 
mammalian life in the swamp shows a rather definite succession, 
depending upon the condition of the land at the different times 
of the year. During the cold, frozen winter the chief inhabi- 
tant is the weasel ( Mustela noveboracensis) and the meadow vole 
( Microtus pennsylvanicus) , living among the dead rushes. The 
vole furnishes the chief food of the weasel, and the signs of many 
a bloody meal have been found on the snow. With the spring 
thaw and the inundation of the land, both of these species retreat 
to the dry edge of the woods, and there await the drying out of 
