Xov.,1913 
REPORT UPON DISEASE AMONG DUCKS 
219 
ago ducks bred in considerable numbers in the San Joaciuin Valley. In 1907, for 
instance, Goldman (Condor, x, pp. 200-205) found conditions favorable for the 
breeding of water birds, and ascertained the nesting' of seven species of ducks. 
But since the lakes and sloughs have undergone such marked changes, and 
since the former feeding and shelter grounds have been destroyed, there is no 
chance for them, and so we now find very few breeding in this part of the state. 
It is impossible to give even approximate numbers of the ducks in the Tulare 
Lake region. Besides the dead there were many thousands of live birds on the 
lake at the time of our investigation. The accompanying photographs (figs. 67 , 
70 ) will give an idea of the numbers of birds which come together on the old 
levees during the day time. The writer feels safe in estimating that there were 
at least a quarter of a million ducks on the lake at the time of the investigation. 
The disease of the present year first appeared during the latter part of July 
and was at the height of its course from about the first to the middle of Septem- 
ber. By the loth of October it was decidedly on the decline. This is in general 
the course of the epidemics of former years. That is, the first appearance is dur- 
Fig. 70. CnOUDS OF DUCKS RISING FROM DEVEE IN TUEARE LAKE; NOTE DEAD AND SICK 
DUCKS IN FOREGROUND, BOTH ON BAND AND WATER; PHOTOGRAPH TAKEN OCTO- 
BER 3, 1913 
ing the very hot summer weather, and the cessation is rather abrupt as the cool 
weather of the fall comes on. 
Special pains were taken to count and estimate the number of dead birds on 
the lake. Our principal observations were taken on the north and west sides of 
the lake, where, it is claimed by some, there was less mortality than on the south 
side. However, it must be noted that the prevailing winds on the lake at this 
time of the year are from north to south ; and therefore this factor may be re- 
sponsible for the greater abundance of dead birds on the south side of the lake, 
because many carcasses are thus doubtless carried across the lake by the wind. 
But because conditions on the north side of the lake were more favorable 
for our work, we selected that side for our purposes and consequently are able 
to give more data from this restricted locality than from elsewhere. The accom- 
panying diagram and table are self-explanatory except that it should be noted 
that the levees, varying in width up to forty feet, are measured from the water 
line on one side of the levee to the water’s edge on the other side. The counts 
