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Table 1. -- Species Composition of the Breeding Population of Ducks, Gray's Lake, 
Idaho, May, 1949 and 1950 
Species Order Percent Composition 
of Abundance 1949 1950 
Mallard : 31 24 
Pintail 19 23 
Canvasback 11 9 
Redhead 10 11 
Teal, Cinnamon a) 8 
Scaup, Lesser 8 9 
Ruddy Duck 5 7 
Gadwall 2 3 
Shoveler 2 3 
Teal, Blue-winged zZ 2 
Teal, Green-winged 1 1 
Ring-necked Duck -- Trace 
Bufflehead Trace Trace 
Baldpate Trace Trace 

Success of the Season 

Goose Production 
During 1950, 204 goose nests were found at the lake. It was estimated by 
means of recheck searches over areas previously covered that approximately two-thirds. 
of the goose nests at the lake were found by the investigators; thus, a total of approx- 
imately 300 goose nests were estimated for Gray's Lake during the 1950 season. Nest 
success for geese was 75 percent and an average hatch of 4.4 goslings per successful 
nest was achieved (see Table 3). Applying the formula, total nests x nest success x 
average hatch, a gosling production of approximately 1,000 was calculated for Gray's 
Lake during 1950, disregarding the influence of possible renesting. 
Duck Nest Production 
On 525 acres of land terrain sampled for duck nests during 1950, a total of 
68 nests were found, giving a nest density of 13 nests per hundred habitat acres of land. 
Since a*reliable nest density figure for land nests was not obtained during the 1949 
season, no comparison between seasons is possible. 
: For ducks nesting over water (marsh samples), twenty-four miles of 
vegetation edge sampled during 1950 produced a nest density of 2.1 nests per mile of 
edge, or 39 nests per hundred habitat acres. Table 2 presents the nest density results 
for over-water nests by species. In 1949, a total of 11.4 miles of vegetation edge was 
sampled and a nest density obtained of 2.5 nests per mile of edge, or 47 nests per 
hundred habitat acres. 
From the following data on over-water nests, it appears that the trend of 
nesting on the marsh between 1949 and 1950 is downward, by about 17 percent, for all 
duck species combined. This decline in nest abundance may be a true reflection of the 
estimated one-fifth decline in the Gray's Lake breeding population which apparently 
occurred between the 1949 and 1950 seasons, as indicated by May population estimates. 
