183 
This investigation has shown that small lakes bordered by sedges and 
willows were by far the most productive. Very few ducks were found to nest on 
the beaver ponds, a possible result of damages by an unusually heavy runoff. 
Repair by beavers was relatively recent, resulting in the creation of ponds not 
present at the beginning of the duck-nesting season. 
Mallards and green-winged teals were the only nesting species on the 
study area (Table XIII). Mallards were most abundant with about 25 pairs present. 
Five pairs of green-winged teal were seen on the sample area. These data indicate 
a breeding-pair density of 1.6 per square mile of study area. 
Final brood counts revealed that 75.9 percent of the breeding population 
successfully produced broods. This resulted in a production of 6.8 young per 
square mile. 
Table XIII - Observed Waterfowl Pairs and Broods on 18 Square Miles of the 
White River Plateau - 1952 


S : Breeding Percent No. of Percent No. of Av. No. Production 
Pech’ Pairs of Total Broods of Total Young per Brd. rere 
Sq. Mile 
Mallard 24 82.76 19 86. 36 102 5.4 a. 7 
Green-winged 
teal 5 17.24 3 13.64 20 6.7 1.1 
Total 29 100,00 22 100.00 122 5.5 6.8 
On the basis of this 5 percent sample it appears that nearly 2,500 ducks 
were produced on the 360 square miles of comparable type on the White River 
-Plateau. 
Summary 
1. Studies were made on six waterfowl breeding grounds in Colorado in 
1952, including three areas covered in 1951. Comparable data for 1951 and 1952 
are thus available for the irrigated land type in northeastern Colorado, for North 
Park and for the San Luis Valley. 
Z. Three heretofore unstudied breeding grounds include the Yampa River 
Valley, Brown's Park, and the high-country lake and beaver-dam type found on the 
White River Plateau. 
3. The 1952 breeding-pair population on irrigated land in the Cache la 
Poudre Valley was about 17 percent lower than for the preceding year. Excellent 
nesting and brood-rearing conditions, however, boosted final production to that of 
1951. 
4. Aerial surveys in 1952 on the South Platte River trend combined with 
a general field observation revealed a large decrease in breeding-pairs, but only a 
small decrease in final production from 1951, 
