DO MOSQUITO-CONTROL TREATMENTS OF WETLANDS AFFECT RED-WINGED BLACKBIRD (AGELAIUS-PHOENICEUS) GROWTH, REPRODUCTION, OR BEHAVIOR

We found no convincing evidence that reproduction, growth, or foraging behavior of red-winced blackbirds (Agelaius phoeniceus) were negative ly impacted by treatments of wetlands with either Bacillus thuringiens is israelensis (Bti, applied as Vectobac-G granules) or methoprene (ap plied as Altosid sand granules). Most red-winged blackbird parameters examined varied annually and some differences were found before treatm ents began. In all cases, differences found before treatments were eit her found again during the treatment years or no patterns existed to s uggest impacts of mosquito control treatments. Only 1 of the 22 variab les examined indicated a significant difference between a treatment gr oup and the controls; males in Bti-treated sites were larger than male s in control sires during the treatment years. Clutch size indicated a significant treatment-by-year interaction and was higher in control a reas as compared with Bti-treated areas in 3 of the 6 years of study; 2 years occurred before any treatments were applied. Data from benthic aquatic insect studies showed that aquatic insects were depressed in wetlands treated with both methoprene and Bti In July and August. Howe ver, it is unlikely that food available to avian species in these wetl ands was lower during the breeding season (May and June). Other portio ns of the avian life cycle that may be affected include the dispersal of young birds within or to these sites and individuals that use wetla nds during migration. Impacts on these aspects of the avian community and landscape-level effects of treatments were not addressed.