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COMPARISON OF AIR AND GROUND WATERFOWL COUNTS ON IRRIGATED 
LAND IN NORTH-CENTRAL COLORADO, 1951 and 1952 
Jack R. Grieb * 
Introduction 
The use of aircraft in determining continental waterfowl breeding 
populations and production has become well established during the last few years. 
There is no question that such a census method is cheap and practical, especially 
where large areas need be covered and manpower is limited. In 1951, a coopera- 
tive study was initiated between the Colorado Game and Fish Department and the 
Colorado Cooperative Wildlife Research Unit for the purpose of determining the 
accuracy of such a census method and its adaptability to Colorado conditions. A 
further objective was to determine if correction factors could be evolved for use 
in aerial waterfowl counts on irrigated lands, so that aerial counts could be adjusted 
to give ground totals. This study was again carried on in 1952, and this report 
represents two years of intensive work on the subject. It is recognized that the 
results of this study would not be applicable to other areas except in principle. 
Grateful acknowledgment is made to Dr. Lee E. Yeager, Leader, 
Colorado Cooperative Wildlife Research Unit, who originally conceived the idea of 
this study, and for help and advice throughout its course. Pilot Kenneth B. Milyard, 
Colorado Game and Fish Department, flew all flights in 1951. Ervin L. Boeker, 
Colorado Cooperative Wildlife Research Unit, assisted with both air and ground 
counts for the two years. Pilot Norman L. Hughes, Colorado Game and Fish 
Department flew all coverages in 1952. 
Area 

The Cache la Poudre study area is composed of Township 7 North, 
Range 68 West, 6th Principal Meridian, Colorado. This area contains a total of 
65.5 miles of waterways in the following breakdown: irrigation canals, 25.9 miles; 
irrigation ditches, 12.0 miles; creeks and drain ditches, 20.2 miles; and river, 
7.4 miles. There are 63.4 acres of sloughs and marshes, and 869.7 acres of 
irrigation reservoirs and natural lakes, both totalling 933.1 acres. 
The area is divided by the Cache la Poudre River, which runs diagonally 
northwest to southeast. It is further drained by several streams emptying into the 
main river. Land-use consists of intensive agriculture. Most of the land is under 
irrigation, with only a small part of the more hilly portion farmed by dry-land 
practices. 
Principal crop types consist of alfalfa, small grains, sugar beets and 
corn, Waste areas are few and scattered, and "clean farming" is practiced by 
most farmers. This involves burning of weeds along irrigation ditches, fence rows, 
and roadsides during late fall, winter, and early spring. The shortage of residue 
cover is met in part by early-growing alfalfa, grass and weeds. Table I lists and 
describes the types found on the study area. 
* Colorado Game and Fish Department. 
