Some observations on the effects of field applications of fensulfothion and parathion on bird and mammal populations.

The application of fensulfothiqn and parathion for the control of invertebrate pasture pests in Canterbury during March, April and May 1970 killed many birds and mammals. Two hundred and thirty-six dead birds were found after a single application of fensulfothion to 123.4 ha, and 158 birds were recovered from 78.5 ha of pasture treated with parathion. The main species killed were white-backed magpie (Cymnorhina tibicen), black-backed gull (Larus dominicanus) and harrier hawk (Circus approximans). Field trials of fensulfothion on 72.8 ha of pasture at Rotorua reduced the bird population using the treated areas by 86 percent within two days of treatment. Most deaths probably occurred through secondary poisoning, although the possibility of primary poisoning through contact or the ingestion of the insecticide granules cannot be discounted