CONSUMPTION OF FIPRONIL-TREATED RICE SEED DOES NOT AFFECT CAPTIVE BLACKBIRDS

Fipronil is an insecticide developed for use on rice seed and other cr ops. In a series of cage and pen trials, we evaluated the responses to dyed, fipronil-treated rice seed of three bird species likely to enco unter it in the held. Individually caged red-winged blackbirds (Agelai us phoeniceus), brown-headed cowbirds (Molothrus ater), and boat-taile d grackles (Quiscalus major) displayed no evidence of adverse reaction to treated seed. Chemical analyses of hulls from treated seeds eaten by captive birds revealed that 10-20% of the fipronil originally prese nt was removed during feeding. In group enclosures, male red-winged bl ackbirds ate as much fipronil-treated rice as they did dyed, untreated seed. In four-day tests within a 0.2-ha flight pen, 10-bird blackbird docks removed 11.4% of fipronil-treated seed from a test plot compare d to 12.5% of dyed, untreated seed removed from the alternate plot. Wh en the alternate plot contained undyed rice, however, seed removal fro m the treated plot averaged 2.4% compared to 28.9% from the alternativ e plot, suggesting that the groups of test birds avoided treated seed based on its appearance. We conclude that 325 and 500 mg kg(-1) fipron il applications alone do not affect avian feeding activity. (C) 1998 S CI.