WATERFOWL BREEDING GROUND SURVEY IN COLORADO - 194% 
Willard L. Flinn*® 
Beope 
San Luis Valley, Nerth Fark, and South Platte Valley areas of Uslorads. 
Feghnigues 
Breeding ground surveys for migratory waterfowl on en extensive acale 
began in Goloredc this year. Aerial survreye were mace in 1948 only in the 
San Luie Valley. 
San Luis Valley 
This area was atudied by beth aerial and inteneire ground surveys in 
1949, For the aerial work the duck nesting habitet wae arbitrarily outlined 
and divided into five parts, esch of different habitat typea, Zeography, and 
land use. These are as followea: Rio Grande River area, 76 square miles: 
Husgell Lakes, 10.5 equare miles; "Potholes," 7&@ square miles; San Luie Lekea, 
10 aquare miles; and farm and meadow land, 1,320 square milee. Total areaa 
were covered in 811 except the meadow and farm land. Here a transect wae 
flown and 4,3 percent of the area wat covered. 
The 1942 nerial brood census wae made br using both transect and 
random eample methode. Hecommendatiane were made to use data by these methods 
as trende for the San Luis Yalley. These flights have been made during the 
eéecond week in July, and expect to continue to be made at the game time of 
year in the future. 
Ground surveys tacluded ceversl etudy ereas selected to sample 10 
ciiferent corer types for the existence of Dreeding paire and non-breeding 
birds, and ta determine number and frequency of nests, clutch size, fate of 
the @@fs, success, and decimating factors affecting production, This study 
hese April] 1 ané continued through 4uguet. Spring wigration data were taken 
according to sex and species, Study areae were carered on foot, and each neat 
located was marked. <All date were recorded and separated ae to especies, corer 
type, date located, condition of neet and eg#a, predator activity, probable 
production or fate of nerts and egea, and other important information. Complete 
Tecordg were made of adult ducks and broods cbeerved. 
Study areac included 10 different cover typea vhich were periodically 
eampled for nests, They include hardstem bulrueh, cattail meareh, grasses and 
erags-like plants, brushlands, native hay meadow, alfalfa, clover, field pear, 
small grains, potatoes and other row crops. 
* The writer wae assisted by Ronald Ryder, who conducted ground surreys in 
San Luis Yalley, by Jack Greib, who conducted ground surveye in South Platte 
River Valley, and ty Aobert G. Kinghorn and Kenneth B. Milyard who apelsted 
dn conducting the aerial censuses. 
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