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Red-winged blackbird; Birds--Effect of insecticides on


We compared red-winged blackbird (Agelaius phoeniceus) reproductive success and nestling growth in 1988 in 10 wetland site treated with methoprene and 10 sites treated with Bacillus thuringiensis israelensis (Bti) to 30 sites that had never received any mosquito (Diptera: culicidae) control treatment. No differences were detected between reference and treatment sites for clutch size, egg volume, growth rates, or fledge weight. The probability that an egg survived to the nestling stage was greater in methoprene-treated than reference sites. No other differences were detected among sites for reproductive success estimated using the Mayfield method. We conclude that treatment of the wetlands with methoprene or Bti did not directly or indirectly affect red-winged blackbird growth or reproduction within the first two years after treatment.

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