Cholinesterase inhibition of birds inhabiting wheat fields treated with methyl parathion and toxaphene

Red-winged blackbirds (Agelaius phoeniceus) and dickcissels (Spiza americana) inhabiting wheat fields treated with 0.67 kg AI/ha methyl parathion and 1.35 kg AI/ha toxaphene showed brain cholinesterase (ChE) inhibition compared with birds inhabiting untreated fields. Maximum inhibition occurred about five days after insecticide application. ChE activities again approached “normal” 10 days after treatment. ChE inhibition for dickcissels and red-winged blackbirds differed significantly (p