Aerial Pesticide Applications and Ring-Necked Pheasants

Abstract

In 1970 aerial applications were made to a 24-hectare section in southwestern Idaho utilizing ethyl parathion in May, demeton and DDT-toxaphene in June, and trichlorfon and demeton in July. Aerial application resulted in a very uneven distribution of chemicals on the ground. Gas chromatographic analysis of residues collected on glass plates during aerial applications showed ranges of 0-2058 ,igrams per plate within the treated area. Observations on penned and radio-equipped wild pheasants (Phasianus colchicus) revealed no direct mortality from the spraying. Penned pheasants 5-15 days old exhibited symptoms of organophosphorus poisoning, but recovered. Cholinesterase and weight gains did not differ significantly in treated and untreated penned pheasants. According to the results of sweep net samples, insect populations were significantly lower in the treated area compared to the untreated area. Juvenile pheasants collected in the treated area consumed significantly fewer insects than birds taken in the untreated area. Applications of certain organochlorines and organophosphorus pesticides probably kill some pheasants, especially young birds, but results suggest that use of demeton, ethyl parathion, DDT-toxaphene, and trichlorfon at recommended application rates does not cause major pheasant losses in southwestern Idaho. J. WILDL. MANAGE. 38(4):679-685 Pesticides, particularly the persistent organochlorines, have contributed to the decline of several species of raptorial and fish-eating birds (Peakall 1970). Organochlorines have also produced harmful effects in the ring-necked pheasant (Azevedo et al. 1965, Baxter et al. 1969). The use of DDT and many other organochlorines has rapidly declined in the pheasant range of southwestern Idaho in recent years. The development of insect resistance and legal restrictions have deleted a number of uses for organochlorines. Organophosphorus and carbamate insecticides have replaced the organochlorines. Some of these chemicals have a high initial toxicity but residue problems are comparatively minor. The organophosphorus pesticides may pose a threat to ground-feeding birds. The pheasant, a ground resident, may be directly harmed by the high dermal and oral toxicity of certain organophosphorus insecticides. Christensen (1969) found that methyl parathion caused substantial mortality of 1to 10-day-old pheasant chicks under minimum exposure conditions. Thus, additional research with other organophosphorus pesticides is justified, especially under field conditions. The objective in this study was to evalu1 Contribution from the Idaho Cooperative Wildlife Research Unit, U. S. Fish and Wildlife Service, Idaho Fish and Came Department, the Wildlife Management Institute, and the College of Forestry, Wildlife, and Range Sciences, University of Idaho, cooperating. 2 Present address: Department of Zoology, the University of British Columbia, Vancouver, British Columbia, Canada V6T iW5. 3 The laboratory portion of the research was supported under Contract 68-02-0552 by the Division of Pesticide Community Studies, Office of Pesticide Programs, Environmental Protection Agency, through the Idaho Department of Environmental and Community Services. J. Wildl. Manage. 38 (4):1974 679 This content downloaded from 40.77.167.21 on Mon, 25 Jul 2016 04:07:01 UTC All use subject to http://about.jstor.org/terms 680 PESTICIDE APPLICATIONS AND PHEASANTS * Messick et al. Table 1. Pesticides applied by fixed-wing aircraft to the spray zone on Gold Island, Idaho, during 1970. Rate of Date of Chemicals and application application concentration (kg/ha) a 22 May ethyl parathion (47%) 0.9 24 June demeton (25%) DDT0.3 (demeton) toxaphene (25% DDT, 2.4 (DDT-) 50% toxaphene) 4.7 (toxaphene) 23 July demeton (25%) 0.3 (demeton) trichlorfon (80%) 1.2 (trichlorfon) a Expressed as active ingredient applied with 46.7 kg H20 per hectare. ate the effects of selected organochlorines and organophosphates on pheasants and their insect food supplies, utilizing both wild and penned birds. We explored the degree of exposure, survival, nesting success, movement patterns, consumption of insects, and cholinesterase inhibition under pesticide-treated and control conditions. We thank the following who helped with various phases of this work: J. Uranga, J. Gabica, H. Homan, B. Wood, V. Bowman, M. Howard, J. Martin, and scouts in Explorer Post 60.