South Platte River Valley 
To give this study area boundaries, a distance of five miles on each 
side of the river was chosen within which the ground survey was made. The 
length was roughly 175 miles. Samples were mapped at intervals of 20 linear 
miles, and 2 sections at each point were sampled, starting with the 2 distal 
sections and alternating to the innermost sections at the next sampling point 
10 miles. Irrigated farm land predominates along the South Platte River, 
except for about 25 miles of range land which was not sampled. A portion of 
the irrigated land was sampled at intervals of 20 miles instead of the 10 miles 
previously stated. 
One township of irrigated farm land east of Fort Collins, Township 7 
north, range 68 west, was intensively studied to attempt to obtain the total 
production. This survey began in early spring to obtain migration data as well 
as nesting results. 
Aerial transects were flown in this large irrigated area to establish an 
aerial trend. It does not seem feasible, however, that the information Sarenned 
by this method can be projected to show production for the entire area. 
North Park 
Total aerial counts were attempted on all major streams and lakes in 
North Park. Heavy cover, especially along streams, made observations difficult, 
and the number of ducks counted is not considered representative of the popu- 
lation. Ground work here was not intensive. Time limited the work. Lack of 
adequate roads and heavy cover did not produce the desired information on sex 
and species ratio as intended. 
Findings 
Aerial Survey 
Effort was always made to sex and determine species while making aerial 
surveys. This was usually difficult because of light variations, cover, and 
speed of the plane combined to hinder the vision needed for such close in- 
spection. The accuracy of sexing was further reduced because nearly grown 
young ducks were indistinguishable from adult females. The species of males 
can be easily determined under certain conditions, and impossible under other 
sets of circumstances. Positive identification of females as to species is 
usually not possible from the air. Mallards predominate in numbers over all 
other ducks, except possibly in North Park. Baldpates, shovelers, gadwalls 
and the divers are more abundant there. Pole Mountain Lake had a high Gonciehe 
tration of baldpates. Lake John showed many divers, such as redheads, scaup, 
and ruddy ducks. Shovelers inhabited some of the shallow ponds. 
Vegetative cover, mainly a heavy growth of willows, was an inhibiting 
factor in counting duck broods along North Park streams, both from the air and 
on the ground. Ducks are always difficult. to see from the air except on open 
water. The aerial count in the northern agricultural area and in the farm land 
of the San Luis Valley was low. Here open water areas are few and small. 
Observation on irrigation ditches and ponds is restricted by trees and other 
cover, 
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