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Field Notes

What the eagles tell us

Eagles, as birds of prey, are top predators in their ecosystems.  Studying their populations gives us information about changes in their habitats and threats to their (and ultimately to our) survival.

By studying the age-structure of migrating Golden Eagles, we can accurately measure the breeding success (and hence food availability) of the birds in Alaska and the Yukon. We can also tell the survival rate of young birds in northern Mexico and southern United States, and this indicates the health of their wintering environment.

Comparison of age ratios of fall migrants with those of the succeeding spring migration gives us information on the survival of juvenile birds on their winter ranges.

Change in median passage dates (the date on which 50% of birds of a population has passed) is demonstrating long-term changes to the climate of western North America.

Satellite telemetry of birds has proved the long distance nature of the migration, with some birds moving great distances on the continent.

For detailed information, please visit the Daily Count Resources page.


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