Reproduction and distribution of bald eagles in Voyageurs National Park, Minnesota, 1973-1993

Biological Science Report 1
By:  and 


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The bald eagle (Haliaeetus leucocephalus) is classified as a threatened species in Minnesota. In 1973, the National Park Service began monitoring the distribution and reproduction of bald eagles in and immediately adjacent to Voyageurs National Park to obtain data that park management could use to protect bald eagles from the effects of use of the park by visitors and from the expansion of park facilities. Thirty-seven breeding areas were identified during 1973-93. Annual productivity ranged from 0.00 to 1.42 fledglings/occupied nest and averaged 0.68 during the 21 breeding seasons. The annual number of breeding pairs tripled, the mean number of fledged eaglets increased 5 times, and reproductive success doubled during the study. However, in more than 15 of the breeding seasons, the mean productivity and the annual reproductive success in Voyageurs National Park were below the 1 fledgling/occupied nest and the 70% reproductive success that are representative of healthy bald eagle populations. We suspect that toxic substances, human disturbance, severe weather, and lack of food in early spring may have kept bald eagles in Voyageurs National Park from achieving a breeding success that was similar to that of conspecifics in the nearby Chippewa National Forest. The cumulative effect of these variables on reproduction and on habitat of bald eagles in Voyageurs National Park is unknown and should be determined.

Publication type Report
Publication Subtype Federal Government Series
Title Reproduction and distribution of bald eagles in Voyageurs National Park, Minnesota, 1973-1993
Series title Biological Science Report
Series number 1
Year Published 1995
Language English
Publisher U.S. Fish and Wildlife Service
Contributing office(s) Columbia Environmental Research Center
Description iv, 28 p.
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