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() Exposure of Free-Flying Birds to Anticholinesterase Insecticides in Two Conventionally Managed Fruit Orchards.
Borges, S1, Vyas, N2, Christman, M1, Hulse, C2, 1 University of Maryland, College Park, College Park, MD, USA2 USGS Patuxent Wildlife Research Center, Laurel, MD, USA
ABSTRACT- Documented wildlife die-offs have occurred following applications of anticholinesterase (anti-ChE) insecticides on managed farmland. Conventionally managed orchards, for example, receive extensive applications of these chemicals throughout the growing season. Because many avian species use orchards for nesting and foraging, they may receive substantial anti-ChE exposure. Most studies of avian risk do not account for differential exposure among species or effects of multiple applications and mixtures of anti-ChEs. These influences need to be understood if avian risk to anti-ChEs in orchards is to be accurately estimated. Exposure of free-flying birds was observed in two conventional orchards during the nesting seasons of 1999 and 2000 and at two reference sites in 2000 and 2001. Our goal was to demonstrate the influences of species and chemical differences on the exposure we observed. Plasma ChE activity and ChE reactivation were measured to identify exposure in several species. Foot washes were collected to determine if a relationship existed between the presence of dermal anti-ChE residues and plasma ChE inhibition. Higher proportions of birds showed exposure at the orchard sites than reference sites. Chipping sparrows (Spizella passerina), American goldfinches (Carduelis tristis), and American robins (Turdus migratorius) demonstrated significantly lower ChE activity compared to references in 1999 (F = 8.00–27.57, p = <.001–.004), and chipping sparrows demonstrated significantly lower ChE activity in 2000 (t = 3.72, p = .002). These species higher proportions of exposed individuals in both years. Residues of anti-ChEs applied in the orchards were detected in foot washes, and the presence of dermal residues differed significantly among foraging guilds (2 = 8.91, p = .01). Because many chemicals were simultaneously present in each orchard, chemical influences on the exposure we observed could not be discerned. This work does demonstrate, however, that birds come into contact with anti-ChEs applied in orchards, and that exposure differs among the species studied. These results underscore the need for multiple species studies, for choosing indicator species on a biologically relevant basis, and for incorporating real-life scenarios into studies of avian risk.
Key words: birds, anticholinesterase insecticides, exposure, species differences
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