The reproductive period, including the time of growth and development of the young, is a highly sensitive time for any animal when physiological systems are acting at critical rates.^Any slight interference, such as the addition of a stressful or toxic agent is likely to be disastrous.^It has been demonstrated that exposure of adult waterbirds or their developing young to slight amounts of petroleum can seriously interfere with the reproductive process.^Effects can range from interference with the physiology of reproduction to killing of embryos, production of developmental defects, stunting of growth and impairment of survival ability when birds are stressed.^Oil can be taken up by adults in their food or picked up on their feathers, and from them can be transferred to eggs or nestlings.^Managers should be conscious of these effects, which though less apparent in nature, may in fact be more serious than the infrequent kill-offs occurring after catastrophic spills.^For it may well turn out that a chronic reduction in reproductive success may be the most significant effect of oil pollution on populations of aquatic birds.

Published in cooperation with the Interagency Energy-Environment Research and Development Program, Office of Research and Development, U.S. Environmental Protection Agency.