Dieldrin Effects in Two Generations of Penned Hen Pheasants

Effects of encapsulated dieldrin fed to penned hen pheasants (Phasianus colchicus) were studied through two generations. First-generation hens received 0, 2, 4 and 6 mg of dieldrin per week for 13 weeks. Hens which were offspring of these 0, 4 and 6 mg treated groups received 0 or 6 mg per week for 14 weeks. Effects of dieldrin were evaluated by measuring food consumption, weight, and egg production of hens, fertility and hatchability of eggs, and survival, weight gain, and behavior of chicks. No mortality occurred in first-generation hens but among second-generation hens there was mortality in all groups receiving dieldrin. None occurred in controls. Food consumption was lower in the 6 mg group of first-generation hens and there was also lower egg production. The same effects were noted in groups of second-generation hens. Fertility and hatchability of eggs were significantly lower in groups where hens received dieldrin via the egg. No effect could be determined on chick survival or weight gain. A group of chicks hatched from eggs laid by hens receiving 8 mg dieldrin most commonly chose the deep side of a visual cliff while chicks hatched from control hens chose the shallow side (P < 0.01). Eggs laid by first-generation penned birds had dieldrin residues averaging 15.7 ppm for the 4 mg group and 33.6 ppm for the 6 mg group. Up to 37 percent of the residue was eliminated from a hen's body when eggs were laid. Residues in fat of six penned hens which survived 2 and 4 mg levels ranged from 18.5 to 45.3 ppm. Dieldrin levels in brain tissue of treated hens which died during experimentation varied from 1.15 ppm to 26.7 ppm. Levels in wild birds were lower than levels found in penned birds.