36 FISH AND GAME COMMISSION 



particularly at Tulare, Tule and Goose lakes and in the lower Klamath 

 Lake region. Tulare Lake, dry for many years, filled with the heavy 

 run-off during the winter of 1937-38 and will continue as a lake until we 

 have a cycle of years of lesser rainfall. Irrigation practices together 

 with the summer heat and decaying vegetation produce ideal conditions 

 for the development of botulism. Water is pumped to preirrigate many 

 thousands of acres in the lake basin. This happens just prior to the 

 arrival of the first wave of migration early in August. Almost imme- 

 diately sick ducks are noted. More and more birds arrive and the con- 

 dition becomes progressively worse until the temperature drops in Octo- 

 ber or November. Some idea as to the duck population can be secured 

 from the estimate made by our field men during the summer of 1940 : 



August 2 12,000 



August 25 100,000 



September 5 350,000 



September 19 800,000 



October 2 1,500,000 



October 14 900,000 



November 6 600,000 



The duck rescue crew must work under the most unfavorable con- 

 ditions. Thousands of acres of disease area covered from a few inches 

 to two or more feet with water but for the most part too shallow for any 

 kind of a boat ; mud sticky and deep ; few roads and a temperature over- 

 head of upwards of 110°. The rescued birds often must be carried for 

 miles to cars that in turn take them to the hospital pens where good water 

 and food are available. During the two seasons of 1940-41, 11,193 birds 

 were picked up and hospitalized. Of these 80 per cent recovered. Most 

 of them were banded and released. On account of the vast area and the 

 adverse conditions under which the rescue crews work, it is probable 

 that less than 10 per cent of the sick birds are picked up. All told, the 

 annual loss throughout the State must run into hundreds of thousands. 



CROP DAMAGE 



Crop damage by game, particularly waterfowl and deer, is not a 

 new problem in California. "With the increase of both species during the 

 past several years, complaints have become more strenuous. Ducks and 

 blackbirds are blamed by rice ranchers for causing extreme losses in the 

 rice fields and in the Imperial Valley not only in the rice but in alfalfa 

 and other crops as well. Blackbirds work during the daytime and can 

 be kept out by the use of a 22 rifle. The ping of the bullet over the field 

 is very effective. Ducks, however, work largely at night and are more 

 difficult to control. Particularly strenuous complaints have been 

 received from the Imperial Valley. One of our field men. Bob Hart, 

 was detailed to the valley to study methods of control. He found that 

 the most effective method was the use of a revolving light that he per- 

 fected. This lis'ht, run from a storage battery, was constructed with 

 gears so that it flashed intermittently. The first difficulty was on 

 account of air beacons. This was overcome by making the light revolve 

 in the opposite direction to the beacon. It was found that one light in 

 the center of a 160-acre field was very effective. With the experience 

 gained the light was improved and several were constructed to use more 

 extensively. Then blackout regulations arose and further experiments 



