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WATERFOWL PRODUCTION AT GRAY'S LAKE, IDAHO, * 1950 - 
Elwood G. Bizeau and Paul E. Steel 
Introduction 
Gray's Lake is a 22,000 acre high altitude marsh located in southeastern 
Idaho, It is characterized by extensive stands of dense, emergent vegetation (mainly 
Scirpus acutus) which covers 90 percent of the marsh proper at high water stage. 
A waterfowl production investigation involving population, nesting and brood 
studies was begun at the lake in May, 1949, and will be continued through the 1951 
breeding season. This investigation is a part of the research program of the Idaho 
Cooperative Wildlife Research Unit. 
The 1949 studies were conducted by Elwood G. Bizeau, research fellow, with 
the part-time aid of George Lea, student assistant. The 1950 population and nesting 
studies were jointly carried on by Bizeau and Pauj E. Steel, research fellow. Brood 
studies and banding operations during 1950 were conducted by Steel, 
Methods Used in Sampling 
Population Counts 
Population figures were obtained from periodic counts at established counting 
points around the lake margin and from foot and boat patrols repeated over fixed routes. 
Goose Nest Production 
Total nest estimates for geese were obtained from a full coverage of the 
accessible open water areas of the marsh by boat and by search of adjacent shore on 
foot. To get an approximation of the number of goose nests not found on the marsh and 
adjoining lands, thorough rechecks were made of selected areas previously searched. 
The number of nests found on recheck searches was then used as an indicator of the 
number of nests normally not found on the remainder of the lake. 
Duck Nest Production 
Nest density estimates for land nests were obtained from a number of small 
block areas selected to include samples of all the main cover types existing near the 
marsh, These areas were worked repeatedly throughout the nesting season with the 
aid of a dog and by rope-dragging. 
Nest density estimates for over-water nests were obtained from random 
samples of vegetation edge established throughout the accessible open-water areas of 
the marsh and worked repeatedly by boat during the nesting season. 
Brood Counts 
Juvenile mortality was measured by conducting brood counts throughout the 
brood season, repeatedly visiting each area of the lake at intervals. Counts were made 
from a powered boat, from a canoe and from foot patrols along the lake margin. Only 
broods accompanied by brood females were counted. 
* A contribution of the Idaho Cooperative Wildlife Research Unit. 
