Regional and habitat differences exist in levels of contamination in Maine 

 eagle eggs (table 16-14). Eggs from western coastal regions have higher mean 

 residues of DDE, DDD, DDT, dieldrin, and PCBs than those of eastern coastal 

 regions. This evidence concurs with the low productivity of bald eagles in 

 western Maine. Residues in eggs from coastal nests tend to be higher than 

 those in eggs from inland sites which may reflect greater contamination in 

 estuarine habitats and/or the higher trophic position of eagles in coastal 

 Maine . 



Limited sampling indicates Maine eagles receive these contaminants from food 

 supplies within the State. Seven of 13 organochlorines present in Maine 

 eagles and their eggs were found in fish and waterfowl samples collected 

 throughout the State. Herring gull carcasses contained all 13 

 organochlorines. DDE, PCBs, and mercury residues are significantly higher in 

 fish-eating species, such as herring gulls and mergansers, than in black 

 ducks. This trophic relationship demonstrates the bald eagle's vulnerability 

 to receiving concentrated doses of contaminants as a result of its terminal 

 position in many food webs. 



Four groups of eagle foods from Maine exhibited significant declines of DDE 

 residues between 1966 and 1974. Trends in PCB exposure are uncertain but 

 stable or increasing levels in fish and pooled black duck wings from Maine 

 have been ci*:ed (White and Heath 1976; Wiemeyer et al. 1978). High mercury 

 levels were detected in livers of mergansers from major eagle wintering areas 

 on the Kennebec and Penobscot Rivers. Point sources of mercury pollution on 

 the Penobscot River and PCBs on the Kennebec River have been cited (New 

 England River Basins Commission 1977). 



The impact of human activity on nesting bald eagles has not been documented in 

 Maine. Nesting success in other eagle populations has been correlated 

 inversely to permanent, visible signs of human proximity. Examples are 

 buildings, roads, boat landings, and timber harvests (Juenemann 1973; and 

 Grubb 1976). Two types of human disturbance have been observed to adversely 

 affect eagle nesting in Maine, i.e., climbing to an active nest, and felling 

 of a nest tree. A dirt road and power line were constructed to within 654 

 feet (20m) of a nest that was active in 1976 but which has since been 

 abandoned. 



Other less visible human activities also may affect eagles. Diminishing 

 quantities of old-growth timber, especially white pine which is preferred by 

 eagles for nesting, may present future problems. Disturbances to nesting 

 eagles are most harmful during incubation (Mathisen 1968) and as eaglets 

 approach fledgling age (Harper 1974; and Weekes 1975). 



Increasing human activity and land development are encroaching upon favored 

 eagle habitats in midcoastal and eastern coastal Maine (regions 4 to 6) and 

 already have modified western coastal areas (regions 1 to 3) formerly occupied 

 by a breeding population. Developmental projects potentially detrimental to 

 the availablity or quality of bald eagle habitats or food supplies, merit 

 careful evaluation, especially those affecting the population center and core 

 of nesting in eastern coastal Maine. 



16-45 



10-80 



