131 
Table 2. ~~ Duck Nest Density on Marsh Samples, Gray's Lake, Idaho, 1950 
’ a a a ee 
Bpeciex , r Total Nests Nests Per Nests Per 100 
Found Mile of Edge Habitat Acres 1/ 
a a 
Diving Ducks 


Canvasback 7 0.29 5.4 
Redhead 20 0.83 15.4 
Ruddy Duck ; 3 0.12 2.3 
Scaup, Lesser 2 2 0.08 1.5 
Sub-totals 32 1.32 24.6 
Dabbler Ducks p 
Mallard a .) 15 0, 62 11.5 
Teal, B-w. &/or Cinn. — 3 0.12 2.3 
Gadwall 1 0, 04 0.8 
Sub-totals — 19 0.78 14.6 
All Species . 2.1 39.2 
1/ Habitat acres for marsh nesting ducks = all edges of emergent vegetation 
to 15 yards in depth from the open water edge. 
Hatching Success 
During the 1950 season, nest history records were completed on 187 Canada 
goose nests and on 213 duck nests of 10 species. Table 3 summarizes the duck and 
goose nesting data obtained during both the 1949 and 1950 seasons, for comparative 
purposes. In some species only a few nests were terminated; information on nests of 
these species is included for its face value. Average hatch figures are computed only 
for those species where 10 or more nests were successful. 
Comparison of nest and egg data between the 1949 and 1950 seasons reveals 
that a much lower egg success (12 percent less) occurred in the Canada goose for 1950. 
In the ducks, a lower egg success ( 5 percent less ) was recorded for 1950 as compared 
to 1949 for all duck species combined. Particularly high nest and egg successes were 
found in the redhead for 1950. 
"An interesting and ecologically important fact relating to goose nesting at the 
lake was that 81 percent of all goose nests found during the 1950 season were situated 
on muskrat houses. x 
Juvenile Mortality 
Not only were less broods observed in 1950 than in 1949, but the average size 
was generally smaller in all three age classes. Several reasons may have been 
responsible for the fewer broods observed:. 1) the known smaller breeding population, 
2) the rank growth of emergent vegetation in areas which last year remained open water 
until after the peak-of the brood season, and 3) the apparent earlier desertion of broods 
by diver females, possibly reflecting the influence of the later nesting season in 1950. 
Table 4 records the brood data for the past two years with the average hatch 
per successful nest given for those species with sufficient nest data. In 1949, 991 brood 
counts were made as compared to only 490 in 1950. Because of the brood counting 
