- Ecological Services
- Endangered Species
- Habitat Conservation
- Wetlands Inventory
|Regional Issue: DDT and PCBs||
Are banned chemicals still impacting Maine's bald eagles?
The Problem and Effects:
DDT was a major reason for the decline of the bald eagle in North America in the 1950s and 1960s. DDT and its breakdown products, DDD and DDE, are toxic to embryos and disrupt calcium absorption and impair eggshell quality.
What We're Doing:
Levels of DDE, a leftover from DDT, have decreased 20-fold in bald eagle eggs. In addition, levels of polychlorinated biphenyls (PCBs) in eggs appear to have decreased at inland areas, but biologists are currently evaluating recently collected egg data from coastal sites. For comparison, biologists have also collected plasma from eaglets being reared at estuarine and offshore island nests since 2009. Levels of DDE and PCB in plasma will be compared to collections from the early 1990s in coastal nest areas.
Mercury levels in eggs collected statewide have stayed surprisingly stable since the 1970s. On average, mercury levels are below suggested toxicity thresholds. Some areas, however, exhibit chronically elevated mercury levels in eggs that could impact reproduction and productivity. Inland, mercury in whole blood from nestlings and adult shed feathers shows a distinctly higher level in nests located on lakes than in nests located along rivers.
Reports on contaminant levels in eggs and on the coastal monitoring are in development and should be available by early 2013.
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July 16, 2015