18 
To extend the area of search, the roads along section lines within 2 miles 
of the area were cruised by automobile in the early morning or evening. This 
gave an incomplete but very rapid coverage of a wider area, For a week in mid 
July, walking tours were made covering all potholes within half a mile of the 
study area. 
Attempts were made to work both early morning and late evening, but this 
proved impracticable and, after a time, evening work was selected as more 
effective than morning. There appeared to be a greater species variation in 
the period of activity in the morning than in the evening since broods were 
seen roosting as mich as an hour after sunrise, while in the evening all were 
active until it became too dark to see. 
aging and Counting Broods —- In addition to the recording of movements of 
marked broods, a roods seen were noted as to species, location, number of 
young, and age. Three age classes were used, as described by Stoudt (190), 
Class I were those young that were still in the dom. Class II were partially 
feathered. Class IIT had nearly all their body feathers but were not yet 
ready to fly. Counts of the number of young were graded as good, fair, or poor. 
In this way, movements of unmarked broods could be traced. If only one brood 
of a certain species, age, and number was seen in the vicinity, and it could 
be repeatedly located, it was assumed to be the same brood. The absence of a 
previously observed brood from a pothole was taken as evidence that it had 
moved away from it, while the appearance of a new brood in a previously checked 
area was accepted as evidence that it had just moved in. These observations 
taken individually are not conclusive evidence of movement, but they occurred 
with such regularity and matched so closely the behavior of marked broods, 
that there seems to be no question of the validity of the information they 
provided. 
Cover Ma -- In order to obtain data on the preference of broods for 
the various vegetative types previously described, cover maps were made of 55 
water areas. These included all the permanent (Group A) potholes, most of the 
semipermanent (Group B) potholes, and a few temporary (Group C) potholes, 
including some on which no ducks were found. Most of the data on these maps 
have been discussed already. Rough estimates were made of the use of the area 
by muskrats, coots, grebes, and black terns. 
Weather Data -= Notes taken in the field contain information on the time 
of ‘day and the weather, Temperature, wind, visibility, and clond cover were 
noted, in order that the effects of these factors on the behavior of the ducks 
might be evaluated. 
IV. MOVEMENTS OF BROODS 
Observed Movements of Individual Broods 
In spite of the small number of broods successfully marked and the 
difficulty experienced in locating them after hatching, the information derived 
from the five broods which were located is of considerable aid in interpreting 
data gained from the population as a whole. 
Included with the following case histories of marked brocds shown in 
Plate X are summaries of information on the movements of individual unmarked 
broods. Only those broods have been included which could be surely recognized 
