THE DELAY IN OVULATION PRODUCED BY pp'-DDT AND ITS POSSIBLE SIGNIFICANCE IN THE FIELD

A significant correlation between pp'-DDT intake by the female Bengalese Finch Lonchuro striata and delay in ovulation is reported. Linked with earlier work showing that pp'-DDT can cause inhibition of the testicular growth and secondary sexual characters of cockerels, it is deduced that in this context the site of action of the pp'-DDT is probably the pituitary or hypothalamus. Inhibition of the secretion of the pituitary hormones could explain the reported recent increase in egg breakages by predatory birds. It is also probable that organochlorine pesticides are responsible for the late breeding of several species of birds reported in the early nineteen-sixties. This could affect a population in that large sublethal doses which double the time for egg laying could cause a double-brooded bird to be out of phase with the food supply for the late broods.