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Organophosphate insecticide (famphur) topically applied to cattle kills magpies and hawks

June 16, 2010

A systematic field study of a black-billed magpie (Pica pica) population revealed that magpies and red-tailed hawks (Buteo jamaicensis) were killed by famphur (=famophos, Warbex®) used as a pouron to control cattle warbles (Hypoderma sp.). Magpie mortality began on treatment day and continued for more than 3 months (38 found dead); mortality peaked between Day 5 and Day 13. Estimates of magpie density (based on transects) decreased in both the control and treatment areas, but the decrease was greater in the treatment area. A red-tailed hawk found dead on Day 10 had eaten a famphur-contaminated magpie. Another red-tailed hawk was found alive but immobilized, and a third died outside the study area. Brain cholinesterase (ChE) activity was 70-92% depressed in all dead birds examined; famphur residues were detected in all 17 magpies and the 2 hawks analyzed. The amount of famphur obtained by the dead magpies was estimated at 5.2-6.1 mg/kg (based on residue concentrations in the gizzard), which was above the acute oral LD50 for several bird species. The cow hair portion (12%) of the pooled gizzard contents from 13 other dead magpies produced extremely high famphur residues (4,600 ppm). The residues persisted on cattle hair for more than 90 days post-treatment. Magpie populations in the far western states declined between 1968 and 1979, which corresponds with widespread use of famphur, although other factors may be involved.

Citation Information

Publication Year 1985
Title Organophosphate insecticide (famphur) topically applied to cattle kills magpies and hawks
DOI 10.2307/3801689
Authors C. J. Henny, L. J. Blus, E. J. Kolbe, R. E. Fitzner
Publication Type Article
Publication Subtype Journal Article
Series Title Journal of Wildlife Management
Series Number
Index ID 5222026
Record Source USGS Publications Warehouse
USGS Organization Patuxent Wildlife Research Center