if,^6 DEC 301925 
No. 13. 
March, 1918 
i "”' r - ' - 4 ; .... . q:ou f 
Swan Lake, Nicollet County, Minnesota as a Breeding Ground 
for Waterfowl 
By Harry C. Oberholser, Assistant Biologist, Biological Survey, 
U. S. Department of Agriculture 
A thorough examination of Swan Lake, Nicol¬ 
let County, Minnesota, was made by the writer, 
July 25 to 27, 1917, inclusive, for the purpose of 
obtaining data regarding its status as a breeding 
ground for waterfowl. The present report con¬ 
tains the result of these investigations. 
Swan Lake is located in the eastern part of 
the great duck-breeding area of the LTnited 
States, and is of sufficient size to be of much 
importance as a resort for game, not only during 
the breeding season but during the autumn as 
well. About one-fifth of the surface of the lake 
is open water, which is apparently in no place 
more than 12 or 15 feet deep. The water of the 
lake is clear and pure, non-alkaline, and in no 
part of the lake at all stagnant. 
Vegetation 
Four-fifths of the surface of the lake are 
covered with vegetation of various kinds, chiefly 
bulrushes and reeds. Plants of many other 
kinds, including shore plants, marsh plants, sub¬ 
merged plants, and floating plants, are numerous. 
This vegetation furnishes abundant cover and 
plenty of suitable breeding places for wildfowl. 
Duck Food 
Few lakes anywhere are as well provided with 
food for ducks and other waterfowl as is Swan 
Lake, both during the spring and summer, as 
well as in the autumn shooting season. At least 
50 different kinds of plants that are valuable as 
food for ducks and other water-birds grow in 
this lake. The general character of this vegeta¬ 
tion can be seen by reference to the accompany¬ 
ing botanical report. Another important food 
supply for water-birds is the astonishingly large 
quantity of small snails which live in the water 
of the lake. Four species are particularly 
abundant, as follows: 
