LEAD POISONIiSrG IST WATERFOWL. 7 



entire liver. This was noticed in particular in examining several 

 whistling swans received at the Washington laboratory from Back 

 Bay, Ya. 



RESULTS OF EXPERIMENTAL WORK. 



During the field seasons of 1915 and 1916 a series of experiments 

 dealing with lead poisoning in ducks was made at a field laboratory 

 near the mouth of Bear River, Utah. Though shot had been found 

 in many instances in the stomachs of birds, their presence had not 

 been determined absolutely as the causative factors of the disease 

 apparent in such individuals. The stomachs of a large number of 

 ducks have been examined in the laboratories of the Biological Sur- 

 vey to determine the food habits of the species. These stomachs 

 were from birds apparently healthy when killed. It is not unusual 

 to find from one to half a dozen or more shot pellets in such stom- 

 achs, and in birds from certain localities pellets were almost always 

 found. These facts cast some doubt on the supposition that ducks 

 were affected unfavorably by eating shot, and it was necessary to test 

 the matter by actual experiment. 



For this purpose small pens 3 feet wide, 3 feet high, and 5 or '6 

 feet long were used. Each pen was placed on a platform a foot 

 above the ground with a hole cut in one end to hold a water pan, and 

 the boards were covered with earth. Ducks were taken from large 

 stock pens and placed in these smaller pens as needed, while control 

 birds were confined under similar conditions in separate pens. They 

 were fed morning and evening on mixed grain containing wheat and 

 barley in equal quantity. 



Wild mallards, captured when young and reared to maturity, were 

 "^sed in the main experiments, so that there was no possibility of 

 their having obtained shot before they were placed under close obser- 

 vation. Shot and lead were given to these birds through a small 

 glass funnel. The lower end of the funnel was placed well down the 

 duck's throat and after the shot were given a small quantity of water 

 was poured down to insure that the pellets or particles should not 

 lodge in the oesophagus. After treatment birds were watched closely 

 for several minutes to make certain that none of the lead was cast 

 out through the mouth. It was found that six pellets of No. 6 shot 

 constituted an amount of lead that was always fatal. Two or three 

 shot were sufficient to cause death in several instances, and as the 

 number was increased the resistance of individual birds decreased. 

 In one experiment two mallards were each given one No. 6 shot. One 

 died 9 days later, while the other was able to throw off the effects of 

 the lead and recover. Pintails and redheads were similarly affected. 

 One male pintail was given four pellets of No. 6 and another six. 



