Bald Eagle Monitoring in the Greater Yellowstone Ecosystem

Research Associate: Michael Whitfield

Project overview: Michael Whitfield has been monitoring Bald Eagle populations in the Greater Yellowstone Ecosystem since 1980 to learn more about nesting productivity and long term research of the species. 

Backstory: Consider the challenges that face a pair of adult bald eagles in order to produce viable young. A young eagle needs about 6 months from the time it hatches to become a top-of-the-food-chain winged predator. That means nesting parents must be on eggs by late February-early March. After an incubation of 32-35 days, the hatchlings will face the elements for about 5 weeks before they have enough feathers to adequately insulate themselves from heat or cold, and April and May can bring more weather surprises. Throughout the nesting season, the adults and growing young must adapt to all the threats of a human-dominated and rapidly changing environment and their own very competitive bald eagle society. 

This is the context for our work at the Idaho/GYE Bald Eagle Research Project. We have been monitoring the bald eagle productivity in Idaho’s Upper Snake River watersheds since 1980 and in that time have collected a uniquely rich database about nesting productivity. In 1983 we monitored 13 bald eagle breeding areas to learn about productivity, band nestlings and learn about breeding territories. In 2013 we tracked bald eagle activity and nesting success at 88 breeding areas–nearly a 700% increase in resident nesting population! We are also tracking the 20% of our adult nesting population that is marked–mostly eagles we banded as nestlings as far back as 1987. These long-lived adults are teaching us about juvenile dispersal, longevity, and breeding area fidelity. 

Bald eagles are no longer a threatened species in our region and are justifiably touted as a successful application of the Endangered Species Act. However, they are an excellent barometer of the health of our area’s major riparian systems in a time of great change. For example, we are observing how eagles respond to changes in early nesting season weather patterns as our climate warms. In 2011, 2008 and 2006 we saw rather dramatic nesting failures at higher elevation nest sites because of severe early spring weather. In years like 2013, when the bald eagles of our region produced at least 84 advanced nestlings, we see the effects of an early warm spring even though foul weather in late spring again impacted higher elevation sites. New nesting pairs, taking up residence in increasingly marginal habitats, are defining the boundaries of their tolerance for human activity and limited prey availability. We observe as the eagles write the next chapter of their story. 

Current Status: Michael and his team continue to carefully monitor the bald eagle population looking at nesting productivity, juvenile dispersal, adult survival and interactions between individual birds. This monitoring contributes to long-term research and observations to learn more about bald eagle behaviors and idiosyncrasies. They work closely with land management agencies and landowners to sustain habitat values. Their findings contribute to several active conservation programs and continue to inform a better understanding of the ecosystem as a whole.

Project Partners:  US Forest Service, Bureau of Land Management

Project start year: 1980

Location: Greater Yellowstone Ecosystem

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