Toxicity of Compound 1080 to Magpies and the Relationship of Dose Rates to Residues Recovered

The acute oral LD50 of Compound 1080 to magpies was estimated at 1.78 mg/kg indoors, 1.91 mg/kg outdoors in summer, and 2.30 mg/kg outdoors in winter. Postmortem 1080 residues were detected in 75 of 76 treated birds. Higher doses yielded higher 1080 residues. Within dose levels, birds surviving longer carried lower residues. In a separate test, an average residue of 0.09 ppm was found in 8 birds treated at 1.59 mg/kg and euthanized 24 h post dosing. The adjusted dietary LC50 of Compound 1080 to magpies tested indoors was estimated at 16 ppm. During LC50 tests, the influence of 1080 on food consumption and bird weight varied. Birds receiving low doses were unaffected and those receiving high doses died quickly. Birds that were affected but did not die quickly, usually lost weight but only slightly reduced food intake. All birds that died had detectable 1080 residue in breast muscle. Birds fed higher 1080 dietary concentrations probably exhibited higher residues postmortem. Our adjusted average LD50 (2.12 mg/kg) appeared somewhat higher than reported in the literature; nonetheless, magpies are very sensitive to 1080. No sex differences were noted. Age, metabolic influences, or cold temperatures, might explain the high LD50 value estimated for winter. The detection of 1080 residue in tissue samples is a useful tool for assessing 1080 exposure in magpies—but it might not be unequivocal. Proc. 15th Vertebrate Pest Conf. (J. E. Borrecco & R. E. Marsh, Editors) Published at University of Calif., Davis. 1992