Mayhew 1950 Mallard 3/a. Conaway Ranch, 2mi. east of Woodland, Yolo Co., Calif. Summary of Field Observations 1948 1949 1950 Territory census (pairs) 400 295 110 No. nests located 60 35 5 Average clutch size 8.4 5.7 8.2 No. broods counted 106 12 4 Average brood size 4.7 4.7 6.2 Aerial census 2,055 210 184 Crop Acreages Crop 1948 1949 1950 Rice 3,400 5,410 2,710 Grain (wheat + barley) 4,310 1,800 5,130 Irrigated pasture 1,640 1,200 1,100 Beans — 360 — Corn — — 900 Flooded land 2,770 500 — Summer fallow 5,500 8,350 7,780 Ditches + roads 1,130 1,130 1,130 Tule swales 55 55 55 Total 18,805 18,805 18,805 In 1949 and 1950 2,4D was used as a spray in the rice fields to control weeds. It was also sprayed in ditches leading to irrigated pastures. Cyanox was used the same years in the same areas.