Food chain aspects of chlordane poisoning in birds and bats.

Abstract

We have observed recurring chlordane poisonings of large numbers of common grackles (Quiscalus quiscula), European starlings (Sturnus vulgaris), and American robins (Turdus migratorius) at suburban roosts in New Jersey during the month of July. This paper describes aspects of the food chain uptake of chlordane that account for the periodicity of these poisonings. Chlordane concentrations ranged from < 0.02 to 20.3 microg/g wet weight in 11 soil samples collected from residential lawns and a golf course near one roost. Of the 10 species of insects and soil invertebrates collected from the area, two scarab beetles, the oriental beetle (Anomala orientalis) and Japanese beetle (Popilla japonica), had the highest concentrations of chlordane-related compounds (15.1 and 5.9 microg/g wet weight, respectively). Concentrations in the other eight species ranged from < 0.04 to 1.3 microg/g. Oriental and Japanese beetles collected from a rural location had concentrations of 0.03 and < 0.02 microg/g, respectively. Emergence of adult beetles peaked in mid- to late July, when bird mortality also peaked. Fecal pellets collected near the roost (n = 24) contained the remains of 1-5 beetles each (mean = 2), and scarab beetles accounted for 40% of the total number of insect parts in the stomach contents of common grackles (n = 8). Unlike soil samples, in which cis- and trans-chlordane predominated, beetles contained large amounts of the more toxic metabolites heptachlor epoxide and oxychlordane. Total chlordane-related compounds ranged from < 0.05 to 18.4 microg/g in Japanese beetles collected from 16 sites in New Jersey and 2 sites in Ohio. The highest concentrations were found in beetles from suburban areas and golf courses. We also analyzed brain tissue from insectivorous bats (15 big brown bats, Eptesicus fuscus, and 5 little brown bats, Myotis lucifugus) that were submitted to the New Jersey Rabies Laboratory in late June/July 1998 and 1999 but found to be rabies-negative. We suggest that high concentrations in three of the bats caused debility or abnormal behavior that may have precipitated submission for rabies testing.