Incidence of Lead Shot in the Rainwater Basins of South Central Nebraska

Substrate samples were taken from eight marshes in southern Nebraska during the summers of 1985 and 1986 when the marshes were relatively dry. Each sample was 12 inches square by 2 inches deep. The number of samples per marsh ranged from 66 to 112, with transect lengths ranging from 71 to 201 m. Based on a 97.5 % recovery rate, these marshes contained an average of 47,217 lead and 5849 steel shot per hectare. Ranges were from 20,690 to 90,286 pellets per hectare for lead and 0 to 14,044 pellets per hectare for steel. Ingestion of spent lead pellets resulting in lead poisoning of waterfowl is a long-recognized phenomenon (GrinnelI894, 1901; Hough 1894; Phillips and Lincoln 1930). The U.S. Fish and Wildlife Service (USFWS), in 1976, estimated that 2.7 million kilograms of lead shot may be deposited in lakes and marshes of the United States each year. Ingestion of this shot by birds can lead to death. Lead poisoning may result in a 2-3% annual loss to the North American waterfowl population (Bellrose 1959). The area selected for this study was the Rainwater Basin of Nebraska, which is a region of palustrine wetlands in the south central portion of the state. This area is characterized by 0.5to 405-ha marshes, which are often dry for part of the year, that serve as migratory and spring staging areas for 5 to 7 million waterfowl (USFWS and Nebraska Game and Parks 1986). Steel shot has been required for waterfowl hunting since 1978 on these wetlands. Initially, however, steel shot was available only in 12 gauge shells, and lead shot was allowed for other gauge shells. In 1980, steel shot was required for all waterfowl hunting on these areas, in 1982 it was required for all shotgun hunting on public wetlands, and in 1986 steel shot was required statewide for all waterfowl hunting. Even with the implementation of these regulations, lead shot may remain available for many years (Bellrose 1959, Wycoff et al. 1971). Lack of data on the amount of steel versus lead shot that may be available to waterfowl in Nebraska wetlands, along with the suspicion of sublethal lead poisoning in conjunction with our annual fowl cholera die-off, prompted this study.