year-round basis. Twenty different species of waterfowl and seabirds are 

 represented in the food remains and more than 50% are black ducks and gulls. 

 Food-debris data are biased somewhat and underrate the incidence of fish 

 because fish remains are digested or decompose rapidly. 



Reproduction 



Bald eagles are believed to mate for life. They exhibit high fidelity to 

 their breeding sites. An individual pair may have several alternate nests but 

 the same nest frequently is used in successive years. The distance between 

 nests within a breeding area averages 0.9 miles (1.5 km) in Maine. 



Some adult eagles are on territory by 25 February in coastal Maine. 

 Prenesting activities include courtship flights and repairs or additions to 

 the nest. The nest framework is constructed of limbs and branches of trees. 

 Finer materials are used to line the nest interior. Over the years eagle 

 nests become quite large. In Maine, nest size averages 5 feet (1.5 m) in 

 diameter and 3 feet (1.0 m) in depth but ranges up to 10 feet (3m) and 17 feet 

 (5m), respectively. Most eagle nests are built below the tops of trees but 

 their bulk may eventually girdle and kill the treetop. 



Considerable intraregional and interregional variation in the timing of 

 reproduction is evident among eagles breeding in Maine. In coastal areas a 

 clutch of 1 to 3 eggs is laid between early March and mid-April. Both adults 

 brood the eggs but the female predominates throughout the 35-day incubation 

 period. Incubation begins with the first egg laid, so hatching is staggered 

 and siblings may differ in age and size. The time of hatching ranges from 

 mid-April to mid-May. Eaglets remain in the nest for 10 to 13 weeks before 

 making their first flights. Fledging dates occur potentially from mid-June to 

 early August on the coast. Family groups may remain together into the fall 

 before the young disperse. 



Natural Factors of Abundance 



Considerable habitat is available to bald eagles in coastal Maine, as 

 evidenced by nearly 263,417 acres (106,647 ha) of inland wetlands (preliminary 

 data of National Wetlands Inventory) and 4000 miles (6400 km) of irregular 

 coastline. Natural limitations on eagle abundance are exceeded by limitations 

 resulting from human activities. For example, habitat and food availability 

 generally are not limiting, but modifications of the environment by people 

 lowered habitat quality and contaminated the diet of eagles. 



Inherent characteristics of the species, including recruitment, reproductive 

 potential, and survivorship, limit the ability of bald eagles to recover from 

 population declines. Field observations imply a lack of surplus nonbreeding 

 adult eagles in Maine. A low reproductive potential, averaging only 1.3 

 fledglings/nesting attempt, is characteristic of eagles even in relatively 

 healthy Alaskan populations (Chrest 1964; Hensel and Troyer 1964; and Robards 

 and King 1967). High postfledging juvenile mortality is indicated by 

 estimates of only 10% to 20% survival through 3 years of life (Sherrod et al. 

 1976; and Gerrard et al. 1978). Bald eagles do not attain maturity until the 

 4th or 5th year of life. 



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