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Nov.,1913 REPORT UPON DISEASE AMONG DUCKS 219 ago ducks bred in considerable numbers in the San Joaquin Valley. In x9o7, 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 xvere many thousands of live birds on the lake at the time of onr 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 xvriter 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 Ioth of October it xvas 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. CLOUDS OF DUCKS RISING FROM LEVEE IN TULARE LAKE; NOTE DEAD AND SICK DUCKS IN FOREGROUND, BOTH ON LAND 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 xvere taken to count and estimate the number of dead birds on the lake. Our principal observations xvere 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 donbtless 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 accotn- 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