apparently by black terns which had a nesting colony on the area and defended it 
against all comers. These birds tad all suffered cuts and bruises on the backs 
of the head and neck. In spite of this, the area was heavily used by all found 
species mentioned. “ujitability in other respects apparently outweighed the dis- 
advantages of possibly competing species. These results are similar to those of 
Munro (1939) who concluded that loons, holboell's grebes, and coots were not a 
major factor influencing the use of water areas by ducks. 
Table 1). Maximum known concentrations of broods on the study area. 
~~ Pothole Broods 

Breods in pothole Pothole size per 
nunber (Acres) acre 
Groups of a single species 
3 mallard 1 10.9 0.3 
2 mallard 17 1.8 1.1 
2 mallard 15 1.2 1.7 
2 mallard 7 0.8 2.5 
2 pintail Fal 201 1.0 
 pintail 33 3.9 1.0 
l, blue-winged teal 1 10.9 0.4 
2 blue-winged teal 2h 1.9 lel 
2 baldpate 33 3.9 0.5 
3 redhead 35 2.6 1.2 
S canvasback 1 10.9 0.5 
3 canvasback 33 309 0.8 
2 canvasback 21 2.5 0.8 
3 canvasback 22 3.0 1.0 
2 canvasback 2h 1.9 Ber 
3 canbasback 0 2.3 1.3 
h ruddy 1 10.9 0.4 
2 ruddy 5 5.0 Ook 
: Groups of all species 
1 mallard, 1 green-winged teal, nue= 
winged teal, 1 shoveller, 1 canvas- 
back, l ruddy 1 10.9 1.1 
1 biwe-winged teal, 1 baldpate, 3 red- 
head, 1 canvasback, 1 ruddy 35 2.6 2.7 
‘1 mallard, 1 pintail, 1 blue-winged 
teal, 1 baldpate, 1 shoveller 20 1.6 3.1 
1 mallard, 1 pintail, 1 blue-winged 
teal, 1 baldpate, 1 canvasback 10 Lely 3.6 

Human Intrusion -- Disturbance was generally kept at a minimum throughout the 
study, amd the influence of disturbance on the movements of broods could not be 
accurately evaluated. Several examples may shed some light on the question. On 
July 14, 2 hours were spent with the aid of an assistant in attempting to capture a 
marked redhead brood on pothole No. 35. This was done by driving them into the 
narrow end in order to capture them by hand. This brood was not driven out and 
remained in the pothole until August 13 in spite of the disturbance. There were 
five other broods in the pothole at the time, one each of redhead, mallard, canvas- 
- back, vintail, and blue-winged teal. The mallerd and redhead broods remained until 
July 21, but the other three were not seen again, Whether the disturbance was the 
orimary cause of the departure of the latter is not known. 

33 
