Abstract

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Guinn, J.E. 2004. Bald eagle nest site selection and productivity related to habitat and human presence in Minnesota. Ph.D Dissertation, North Dakota State University. 172 pp.

Abstract:

Removal of the bald eagle from the federal Endangered and Threatened Species List has been proposed but delayed, pending consideration of habitat needs and the development of a population-monitoring plan. This project evaluated the species' use of nesting habitat in Minnesota, where a large population of bald eagles nests across several different ecoregions and near varying levels of human activity. A total of 24 habitat and human-presence variables were measured at a sample of 120 active nest sites and 166 random sites. Measurements within 100 m of nests were taken on site while variables up to 1,000 m were measured by analyzing remote-sensing data and aerial photographs. Discriminant Analysis separated nest sites from random sites primarily on the basis of tree diameter and distance from shoreline. Information-theoretic Model Selection showed little relationship of productivity at each nest to the characteristics of the site. Within the range of basic requirements (proximity to water, substantial trees for nest support, and an adequate prey base), eagle habitat was highly variable and not specialized. The rebound of bald eagle populations did not occur with concurrent increases in habitat. Rather, it appears that recent population trends were the result of demographic factors that were probably not related directly to habitat or human presence. As long as the public does not harass the birds or impact eagle reproduction and survival, nesting bald eagles appear to coexist satisfactorily with humans in close proximity. The continued welfare of bald eagles depends most importantly on protection of the birds themselves, via continuing education of the public and enforcement of existing regulations. While bald eagle nesting habitat should not be ignored, there is little evidence from this study that it is currently a major concern in the state of Minnesota.


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