57 
The count was made from an air-thrust boat on May 21, which was after 
most of the migrant birds had departed and before the arrival of the summering 
population, It was conducted along the 13 miles of shoreline where visibility was 
not impaired by dense vegetation. The average pair and lone drake count per mile 
was 4,0 blue-winged teal, 2.2 gadwall, 2.0 mallard, 1.9 shoveler, 1.7 pintail, and 
0.5 baldpate for a total of 12.3. An influx of paired birds the first part of June 
altered the figures and probably resulted in a change in the species composition and 
density of -the breeding population around the entire lake. 
Intensive nesting surveys were conducted in each of the following cover types: 
1, The extensive whitetop marshes that adjoin the lake on the 
east and southwest. 
2. The emergent vegetation of the lake proper. 
3. The prairie vegetation bordering the lake. 
4. The shrub vegetation (Symphoricarpos occidentalis, dominant) on 
the 210 acre Island. 
5. The farmland within one-half mile of the water's edge. 
The whitetop marshes provided nesting cover for several species of ducks 
and was the preferred cover of redhead, pintail, and ruddy. Known nest density was 
as high as 110 to the quarter section in the best area. 
The sparse emergent vegetation of the lake proper was only slightly utilized 
by breeding diving ducks. An intensive search throughout the nesting season located 
only three redhead and two ruddy nests. 
The prairie vegetation of the dry portion of the old lake bed and the farmland 
surrounding the lake supported a nesting population approaching the figure of 12.3 
pairs and lone drakes per mile of shoreline obtained by the air-thrust boat count, 
The dense shrub stards on the Island were the preferred nesting cover for 
baldpate, and gadwall, and were utilized by all species of dabbling ducks nesting on 
the lake. Known nest density was one nest to eight acres. 
A total of 327 nests were located in the 5 cover types. Nest success based 
only on positive hatches and positive desertions and destructions was 33 percent. 
Brood surveys were conducted from the water using an air-thrust boat and 
from the land by walking portions of the lake shore. A total of 164 brood observations 
were made on the lake proper between June 29 and August 31. All attempts made to 
survey broods in the dense whitetop marshes failed, but on several occasions injury- 
feigning hens were flushed. 
The figure of 164 includes every brood seen regardless of whether it was 
recorded previously. Approximately 72 of the 164 were second and third records, 
making 92 the approximate number of new broods seen. The species composition 
of the 92 broods was 41 blue-winged teal, 16 redhead, 10 gadwall, 9 pintail, 
7 shoveler, 3 ruddy, 2 canvasback, 2 baldpate, 1 green-winged teal, and 1 mallard. 
