An investigation of the toxicity of insecticides to birds' eggs using the egg‐injection technique

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Abstract
SUMMARY: Twenty‐five insecticides have been tested for their toxicity to hen embryos at various concentrations, using an egg‐injection technique. Of the two major groups, the organophosphorus compounds are much more toxic than the organochlorine. Most organophosphorus compounds lower the hatch rate and cause teratogenic effects at 100 ppm. Most organochlorines do not harm the embryo at high dosages (up to 500 ppm), with notable exceptions to this among the cyclodienes. However, starvation of the hatched chicks suggests that the majority of organochlorine compounds can kill at this stage, though fed chicks survive. The solvent used affected toxicity; in general, insecticides are more toxic to the embryo when dissolved in corn oil than when dissolved in acetone. If these findings can be applied to wild birds, it can be assumed that the vast majority of insecticides are harmless to birds' eggs. They are either not toxic in the concentrations so far found in this country, or else unlikely to pass through the mother bird to the egg.