180 
San Luis Valley - In general, the San Luis Valley water levels in 1952 were above 
those of previous years because of high winter precipitation on drainages entering 
the valley. This resulted in increased nesting habitat and consequently a greater 
dispersion of nesting-pairs. 
Results of the 1952 aerial survey is given in summary form in Table X. 
No measured data are available for the 1951 count; however, the 1949 and 1950 
results are offered for comparison. The 1952 aerial survey confirmed previous 
predictions that production would show an increase this year. Not only were more 
broods produced, but significantly more young were found per brood than in former 
years. Thus the production of young was increased by about 35 percent over 1950. 
In a comparison of 1951 and 1952 production, the habitat restrictions 
imposed on the breeding population by the 1951 drought limited nesting to the 
permanent water areas. Beyond a doubt, the unrestricted nesting in 1952 permitted 
a much larger production than in 1951. 
Table X - Comparison of Production in the San Luis Valley, 1949, 1950 and 1952 
Year Number of Broods Number of Young Average Number 
of Young per Brood 
1949 57 353 6.20 
1950 100 522 5.22 
1952 115 809 7,03 
Yampa River Valley - The Yampa Valley is a long narrow floodplain and canyon 
extending from the headwaters of this stream on the White River Plateau to its 
confluence with the Green River in northwest Colorado. The Valley varies from 
1/8-mile in width in the canyons to about 10 miles in width shortly after its 
emergence on to the floodplain proper west of Steamboat Springs. The water table 
along the entire non-canyon portion of the Valley is high, and development of sedge 
and cattail marsh is extensive. This habitat, plus the oxbow and meandering stream 
areas, constitutes the waterfowl breeding grounds found in the region. 
Studies in the Yampa River area were begun in April 1952, Sampling was 
on the basis of 11 2-mile strips at 20-mile intervals, along the 220 mile length of 
the stream. Each strip was 1 mile wide. Observations of adult ducks and broods 
were recorded bi-weekly. Complete data now available for this breeding ground are 
presented in Table XI. 
On this 22-square mile sample, constituting 10 percent of the Valley area, 
a breeding-pair density of 8.7 per square mile was recorded. Brood density was 
6.4 per square mile, giving 1.36 pairs of birds per brood for the sample area. 
Production expressed in number of young produced per square mile was 40.26. 
Projection of these figures reveals that the Yampa Valley produced about 9, 000 
ducks and geese in 1952. 
