110 
WATERFOWL BREEDING GROUND SURVEY IN CALIFORNIA, 1950 
John E. Chattin, A. W. Miller and J. A. Blaisdell * 
Introduction 

During the spring and early summer of 1950 the waterfowl breeding ground 
survey was continued in essentially the same manner as in 1949 throughout the prin- 
cipal waterfowl habitat in the State. By way of review it should be noted that under 
existing conditions the primary waterfowl production area in California lies in the 
northeast or "Great Basin" corner of the State. This area contains numerous natural 
marshes and artificial water impoundments on which over one-half of the ducks in the 
State are raised, The scattered distribution of water areas within this great basin type 
region makes it impossible to fly aerial transects. As a result, this entire area was 
given complete aerial coverage of all water and marsh areas to determine total numbers 
of breeding waterfowl. 
The second important waterfowl production area in the State is the valley of 
the Sacramento River, Under present conditions the Sacramento Valley serves to 
produce about one-fourth of the State-reared waterfowl. The bulk of this area is 
devoted to intensive agriculture with only a remnant of the once vast marshlands 
remaining. These remaining marsh and overflow lands are largely in private owner- 
ship and are controlled primarily by private duck clubs. Coupled with these remnants 
of marshlands the culture of rice as a commercial crop is responsible for a large 
proportion of the waterfowl raised in this area. From late April through the middle of 
September, over 200,000 acres of shallow, stabilized water in the form of contoured 
rice fields are available to nesting ducks. Before the rice becomes too high, this area 
can be ideally covered by aerial transect flights as was done in 1949 and again this year. 
Later in the season, however, brood counting and fall population counts are difficult to 
accomplish due to the dense cover growth and inaccessible nature of these areas on foot. 
In contrast to northeastern California, where a variety of waterfowl species nest, the 
primary species nesting in the Sacramento Valley is the mallard. 
The remaining quarter of the waterfowl produced in California are raised in 
scattered sections of agricultural and marsh habitat, including tidal saltmarsh, stream 
channels and artificial impoundments. These areas include the Suisun marsh, Sacramento- 
San Joaquin river delta, the Grasslands in the San Joaquin Valley. Productivity is high 
on these smaller areas in many cases but is limited in significance by the relatively small 
size of area and amount of water. Production surveys of these minor areas have been 
repeated this year only where time and convenience enabled us to do so. 
Scope and Methods 
Insofar as possible the areas covered, census routes travelled, and methods 
employed, have been duplicated from the pattern established last year. Essentially the 
same observers have been used in each area as were used in 1949. 
All the aerial transects were flown at elevations of 150 feet at speeds of 85 to 
90 miles per hour with two observers covering a ground strip 1/8 mile wide on either 
side of the airplane. Under existing conditions experienced observers were able to 
record accurately the species and sex of those ducks exhibiting divergent sex character- 
istics as well as note whether the birds occurred as pairs, singles, or groups of males, 
* Personnel of Federal Aid in Wildlife Restoration Project California 30-R cooperated 
in this study. Credit is also due the various waterfowl refuge supervisors of both 
State and Federal Refuges in California for lending assistance in gathering certain 
of the field data. 
