
198 
Discussion and Conclusions 
parte pg TUTE oe IE A eT TF eB OO PO OT ETS aE PG OTE LA 
Tables 1 and 2 portray a summary of the results of waterfowl breeding 
grounds census work for the spring of 1950 in Wisconsin. Four types of census work 
were done ahd are reported here, namely: 
1. Cross-country automobile transects. 
2. Cross-country aerial transects. 
3. Aerial lake and marsh surveys. 
4. River surveys. 
As noted above, square miles on all the types of census were computed on the 
basis of 1/4-mile strips. The lake and marsh and the river surveys consisted almost 
entirely of shoreline checks flown at a distance of 220 yards from the shoreline. 
Census routes followed were practically identical with those depicted on the 
map submitted with the 1949 report; consequently, no map of census routes accompanies 
this report. Although each region of the State is not represented on a basis commen- 
surate with its size, yet census routes do cover over 50 of the State's 71 counties, 
Distribution of census routes tends to favor those areas which have proved to be more 
prolific duck producing areas in order to preclude the possibility of statistical error 
in evaluating population trends. Since Wisconsin's waterfowl habitat is relatively poor 
from the standpoint of local duck populations when considered on a State-wide basis, 
the aforementioned tendency to favor better areas is therefore a practical necessity if 
our census work is to be worthwhile in view of the limitations in manpower and funds 
provided to the waterfowl research project. 
In general, the data presented in each of the above tables depict trends well. 
However, the following general explanatory comments and conclusions are offered for 
the guidance of the reader: 
1. The waterfowl breeding population declined in Wisconsin in 1950. Ground 
and the lake and marsh surveys indicated comparable breeding densities with 1949, but 
river surveys and cross-country aerial transects indicated sharp declines. When we 
take into consideration the fact that several changes in method of operation and of 
computation tend to favor the 1950 data, slight though it may be, the conclusion that 
local duck and coot populations decreased is inescapable. 
2. The total number of waterfowl on Wisconsin waters covered during the 
spring breeding grounds census increased. This increase is largely attributable to 
an increase in the transient diving duck population, or, expressed otherwise, toa 
delay beyond their usual spring departure dates, That late breeding species of puddle 
ducks (e.g., blue-winged teal) were often flocked and that they may have subsequently 
paired, selected territories, and nested in Wisconsin is a definite possibility. However, 
work conducted during the subsequent waterfowl production survey showed a sharp 
reduction in numbers of local teal, suggesting that the aforementioned flocked birds 
left the regions where censused and moved elsewhere. 
Consequently, the slight increase in total duck numbers in Wisconsin during 
May seems directly attributable to a late spring migration. 
3. The coot population in Wisconsin in May showed a perceptible decline 
when compared with data from 1949. 
4. It was evident from an examination of data on species composition that 
the common mallard decreased most markedly with the black duck apparently parallel- 
ing the mallard decrease. Blue-winged teal at least held their own statistically and 
may have increased somewhat. The ringneck, Wisconsin's most common breeding 
diving duck, maintained the same breeding level as 1949. Other diving duck species 
