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The effect of orchard spraying on pheasants in the Okanagan valley, with observations on bird-life in orchard areas Benson, Walter Arthur

Abstract

A review of the current literature on DDT and reports from sportsmen and growers indicated that the concentrations of DDT used in the Okanagan Valley were greater than those experimented with previously. Further, that many other insecticides possibly detrimental to wildlife were in use in the Okanagan. A recent decline in pheasant populations was attributed to orchard spraying by many interested persons. The present investigation is of a preliminary nature and set out to determine: 1. The effect of orchard spraying on pheasants. This was done by means of controlled experiments wherein pheasants were placed in orchards during the normal course of orchard spraying. 2. The residual effect of toxic spray materials. This was done by subjecting pheasants to a period of starvation some time after they had been sprayed. 3. The effect of orchard spraying on wild-life other than pheasants. This was done mainly by field observations. 4. Whether or not the recent pheasant decline was due to orchard spraying. This was also done mainly by field observations. It was found that Parathion with DDT, Parathion, DDT, Hexafoss and Lindane were toxic to pheasants while Mono DN was apparently non-toxic. Inhalation exposures are probably more toxic than ingestion exposures and older birds are apparently more susceptible to both exposure types than are young birds. This 13 thought to be a reflection of the feeding habits of the two age groups. A residual effect was not observed for any of the insecticides tested but the data was not conclusive. Robins, bluebirds and song sparrows are the avian species most affected by orchard spraying. Which sprays are the most toxic is not known at present although Parathion apparently does not harm robins. The mourning dove and California quail are apparently not affected by orchard spraying. Chemical analyses by the total chlorine method do not furnish adequate evidence of death from toxic sprays at the present time. Too many variables are evident that possibly alter the toxic effect of the spray material. The recent pheasant decline did not result from orchard spraying although this practice may have aided decline. The reason for the decline is not known, many theories have been advanced but they are not wholly valid. The conclusion reached is that the pheasant population characteristic is not flat but shows fluctuations which may later prove to be cyclic when more information is available. Several suggestions for future studies, concerning orchard spraying, are made. It is hoped that the biologists will keep pace with insecticide development.

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