Contaminant Burdens and Reproductive Rates of Bald Eagles Breeding in Maine
- Welch, Linda J.
The Graduate School, University of Maine
Contaminant investigations conducted on bald eagle (Haliaeetus leucocephalus) eggs collected in Maine in the 1970's and 1980's reported significant levels of environmental contaminants. Many of these contaminants have been correlated with reduced reproductive rates in bald eagle populations. Within Maine, eagles have never reached the production level of 1.00 young/occupied nest, associated with healthy populations. the Maine bald eagle population continues to exhibit reproductive rates consistently below levels achieved by all other major populations of eagles.
To determine current contaminant exposure in the Maine bald eagle population, eggs and nestling blood and father samples were collected during 1991 and 1992. Samples were analyzed for organochlorine pesticides, PCBs, TCDD-EQ and mercury. Brain and liver samples were collected from eagles recovered within Maine.
Contaminant residues and production rates varied significantly between habitat types. PCB and DDE concentrations were significantly higher in nestlings sampled along the coast of Maine. In contrast, mercury concentrations in both blood and feather samples were significantly higher in eagles samples from inland nest sites. eagles nesting along the coast experienced a significantly higher rate of production that n eagles nesting in interior regions of Maine.
Significantly elevated concentrations of mercury, PCBS, DDE, and TCDD-EQ were observed in the Maine bald eagle population. Contaminant concentrations observed in this study exceed levels associated with reduced reproductive rates in bald eagles. Results indicate that environmental contaminants are limiting the reproductive capabilities of the Maine eagle population.
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