We reviewed the U.S. Geological Survey National Wildlife Health Center (NWHC) mortality database from 1980 to 2000 to identify cases of
poisoning caused by organophosphorus and
carbamate pesticides. From the 35,022 cases from which one or more avian carcasses were submitted to the NWHC for necropsy, we identified 335 mortality events attributed to
anticholinesterase poisoning, 119 of which have been included in earlier reports.
Poisoning events were classified as confirmed (n = 205) when supported by findings of > or =50% inhibition of
cholinesterase (ChE) activity in brain tissue and the detection of a specific
pesticide in the gastrointestinal contents of one or more carcasses. Suspected
poisonings (n = 130) were defined as cases where brain ChE activity was > or =50% inhibited or a specific
pesticide was identified in gastrointestinal contents. The 335 avian mortality events occurred in 42 states. Washington, Virginia, and Ohio had the highest frequency of events, with 24 (7.2%), 21 (6.3%), and 20 (6.0%) events, respectively. A total of 8877 carcasses of 103 avian species in 12 orders was recovered. Because carcass counts underestimate total mortality, this represents the minimum actual mortality. Of 24 different pesticides identified, the most frequent were
famphur (n = 59: 18%),
carbofuran (n = 52; 15%),
diazinon (n = 40; 12%), and
fenthion (n = 17; 5.1%). Falconiformes were reported killed most frequently (49% of all die-offs) but Anseriformes were found dead in the greatest numbers (64% of 8877 found dead). The majority of birds reported killed by
famphur were Passeriformes and Falconiformes, with the latter found dead in 90% of
famphur-related
poisoning events.
Carbofuran and
famphur were involved in mortality of the greatest variety of species (45 and 33, respectively). Most of the mortality events caused by
diazinon involved waterfowl.