177 
Evaluation of production by cover types shows that many more broods 
were produced on the river in 1952 (Table V). This corresponds to the findings 
of the breeding-pair survey. Although breeding-pairs were increased on the 
slough type, production was not greater this year, probably because of a severe 
hailstorm which filled sloughs and destroyed nests. 
When considered over the three-year period, sizable water bodies such as 
lakes and reservoirs were most important with canals and Sloughs ranking second 
in production per square mile. Irrigation ditches and the Cache la Poudre River 
were fairly important as nesting sites during 1950 and 1952, but relatively 
unimportant in 1951, 
Final calculations reveal that 75.9 percent of the breeding pairs success- 
fully produced broods in 1952. This success ratio was much higher than in 1951 
when only 62.6 percent of the breeding-pairs were successful. No comparative 
data are available for 1950. 
South Platte Valley - Due to insufficient time and manpower it was impossible to 
cover the South Platte study sections as in past years. Rather, all information 
presented here is based on aerial trend counts for 1951 and 1952. This two-year 
summary is tabulated in Table VI, and reveals that breeding-pair numbers in 1952 
were fewer than in 1951. The comparison, however, is affected by two major 
uncontrollable factors. In 1951, the water level of the South Platte River was low 
as compared to 1952; secondly, nesting season in 1952 was advanced by about 
10 days. These facts alone would partially account for the high number of ducks 
seen in 1951 because migration was probably still in progress on the date of the 
plane coverage. 
Aerial brood counts in 1951 and 1952 show that the earlier 1952 ’enumeration 
was much less than 1951. A later count gave totals very similar to those of 1951; 
however, it is doubtful whether either of the 1952 flights were comparable to 1951 
because of phenological differences between the two years. 
_ General observations in the South Platte Valley tend to clarify the results 
of the aerial surveys. Without question there were fewer breeding-pairs in the 
Valley this year; however, it is believed that the excellent nesting and brood-rearing 
season permitted final production figures to approach those of 1951. 
Table VII - Aerial Brood Counts, South Platte River, 1951 and 1952 
No. of Broods No. of Young Av. No. Yg./Brood 
1951 1952 1951 1952 1951 1952 
Area Mid-  Mid- Barly Mid- Mid- Early Mid- Mid- Early 
July July Aug. July July Aug. July July Aug. 
Denver - Greeley 4 3 2 19 9 9 4.8 3.0 4.5 
Greeley-Ft. Morgan 4 2 10 14 #13 47 3.5 6.5 4.7 
Ft. Morgan-Sterling 7 4 4 24 8620 20 2.8 5.0 5,0 
Sterling -Julesburg 16 12 15 91 53 82 Bol 4.4" (525 

Total 31 21 31 148 95 159 4.8 4,5 5.1 
