Summary

Description

Reproductive success of American white pelicans Pelecanus erythrorhynchus was monitored at a nesting colony on Anaho Island, Pyramid Lake, Nevada in 1996. Eggs were collected and analyzed for organochlorine pesticides OCPs, total polychlorinated biphenyls PCBs, and an array of metals and trace elements, including mercury Hg and selenium Se. Blood samples from 2weekold nestlings were analyzed for Hg and Se, and samples from prefledging nestlings were also analyzed for Hg and Se plus other metals and trace elements. Livers from adult pelicans found dead and a few prefledging nestlings that were euthanized and necropsied were also analyzed for metals and trace elements. Muscle samples of adults also were analyzed for OCPs and PCBs. Fishes from representative feeding areas and regurgitate samples from nestlings were collected and analyzed for OCPs, PCBs, and an array of metals and trace elements, including Hg and Se, to determine levels and sources of contamination to breeding pelicans. Similar sampling activities were conducted at a reference colony at Malheur National Wildlife Refuge NWR, Oregon. Reproductive success at the Anaho Island colony was normal based on hatching rates of eggs and survival of nestlings. Organochlorine pesticide and PCB concentrations in eggs were below known effect levels, with biologically insignificant shell thinning. Organochlorine pesticides and PCBs were seldom detected in fish, but OCPs were elevated in muscle samples of 20 of adult pelicans. Mercury concentrations in eggs were generally below known effect levels, as were concentrations of other metals and trace elements. Metal and trace element concentrations in fish ranged widely for some constituents, with Hg of greatest concern. Microscopic lesions of Hg toxicity were absent in prefledging nestlings that were euthanized. Some adult pelicans had elevated Hg concentrations in their livers; however, the potential toxic effects were difficult to evaluate because the proportion of methylHg declined as total Hg concentrations increased, thereby possibly providing protection from toxicity.