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Weather and Water Conditions 
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The spring thaw at the lake was 10 to14 days later during 1950 than in 1949. 
The later arrival of spring at this high altitude (6, 400 feet) apparently did not alter 
the time pattern of nest establishment for Canada geese. In 1950, the peak of nest 
establishment for geese occurred April 16-20 when only a small part of the lake was 
ice-free, For comparison, brood counts and nest hatch dates on geese in 1949 showed 
that the peak of nest establishment occurred April 19-24. - 
Nest records and brood observations on ducks indicated that the peak of nest 
establishment occurred from one to two weeks later in 1950 for the early nesting duck 
species at Gray's Lake (mallard, pintail, canvasback and redhead) as compared to 
1949. 
Aside from the chronic lack of interspersion of water and vegetation on 
Gray's Lake marsh, water conditions for nesting were excellent during the 1950 
season. Run-off from the small creek watersheds feeding the lake was gradual and 
there was no evidence of loss of waterfowl nests from flooding. Comparison of gauge 
measurements taken throughout the nesting seasons of 1949 and 1950 shows that the 
lake level remained approximately one-half foot higher throughout the 1950 nesting 
season than it was in 1949, 
The lake level dropped 1.72 feet from May | to September 1, 1950, with 
consequent severe shrinkage of the open water areas available to broods, Water 
records for previous years indicate that this marked water loss occurs annually at 
the lake. By August, 1950, most of the broods were concentrated in the few areas 
of the marsh which held water throughout the summer. 
Breeding Population Trends 
Waterfowl Counts 
‘Population counts conducted during the later part of May were believed to 
represent the breeding population of ducks at the lake, since the peak of migration 
for all species had passed by mid-May, 1950. Table 1 presents the species compo- 
sition of the breeding population of ducks for 1949 and 1950. 
A marked decrease in percent composition occurred in only one species, the 
mallard. Pintails show a definite increase in composition. Mallards and pintails 
together made up roughly one-half of the breeding population of ducks in both years. 
From ground counts, total breeding populations of 15, 000 ducks for 1949 and 
12, 000 for 1950 were estimated; these estimates indicate a decline of one-fifth in 
duck numbers between the 1949 and 1950 seasons, This decline indicated by population 
estimates is apparently corroborated by the results obtained in sampling for duck nest 
density on the marsh (Table 2.) and in brood counts. 
In 1950, April counts indicated a total of approximately 1,000 Canada geese 
at the lake. From nest data accumulated during the 1950 season, it was calculated 
that 600 of the 1950 goose population were breeding birds. Groups of (apparently) 
non-breeding geese were observed around the edges of the marsh throughout the goose- 
nesting season. Due to the late start of field studies during 1949, a reliable estimate 
of the breeding population of geese present during 1949 is not available to give trend. 
