1915] Cahn: Ecology of Wingra Springs Region 149 
two species is due to the difference in the conditions existing 
in the associations to which they were migrating. The Spartina 
society thawed earlier under the influence of the sun, and was 
therefore further advanced, and ready earlier to receive the 
avian inhabitants. The quail may well have left the Cornus 
for the Spartina society because the latter was more advanced. 
There was sufficient concealment for so small a bird, while 
the protection offered was insufficient for the grouse. At the 
time the quail was migrating toward the fields, the woods still 
contained patches of snow, and the ground was still frozen. 
VIII. AVIAN ZONATION 
The data accumulated in the study of the birds of the forma- 
tion we are considering show a more or less definite zonation 
of species both in horizontal and vertical planes. There is 
some ground to believe that there is a zonation in each of the 
typical associations in each of the above-mentioned planes, 
but the writer has confined himself to working out the align- 
ment of the species in the horizontal plane in the water, shore, 
and marsh associations, and offers, the results of this phase 
of the work, with a few remarks on vertical zonation. 
Horizontal Zonation 
The various species of birds can be grouped into reasonably 
distinct zones. Starting with the central portion of the lake, 
we find extending toward the shore and the region beyond, more 
or less concentric zones which are characterized by the presence 
of one or more species of birds. Thus the ruddy duck, the blue- 
bill, the golden-eye, and the loon are found to be most at home 
in the middle of the lake: at least they show a marked desire 
to keep as far away as possible from the shore-line. The next 
zone is characterized by the pied-billed grebe and the horned 
grebe, these being found most commonly in the area lying be- 
tween that occupied by the preceding species of ducks and the 
shore region. Immediately about the shore we find such species 
as the coot, mallard, pintail, baldpate, which seem to prefer 
this more sheltered and protected region to the more open and 
deeper water. These shore species are for the most part poor 
divers if compared with the species found in the deeper water 
zones. 
