More Than 316,000 Bald Eagles Live in the Lower 48, New Estimate Says
By Gustave AxelsonBald Eagle by Matt Davis/Macaulay Library. March 24, 2021
From the Summer 2021 issue of Living Bird magazine. Subscribe now.
Revised June 25, 2021
For the past 50 years, the U.S. Fish and Wildlife Service has been assembling counts of Bald Eagle nests from the states and by aircraft surveys to track the triumphant population recovery of America’s national symbol. But in its new Bald Eagle population report—tabulated with the help of results using eBird data from the Cornell Lab of Ornithology—the USFWS found many more eagles than previously thought to exist in the Lower 48 states.
A lot more.
The latest USFWS Bald Eagle Population Update report estimates 316,708 eagles across the contiguous United States, which is more than quadruple the eagle population reported in the 2009 report. The rising number of Bald Eagles undoubtedly reflects the continuing conservation success story that stretches back to the banning of DDT in 1972.
“This is truly an historic conservation success story. The Bald Eagle has always been considered a sacred species to American Indian people [and] sacred to our nation as America’s national symbol,” said U.S. Interior Secretary Deb Haaland at a press conference on March 25. The Bald Eagle population report announcement marked the first public appearance after Senate confirmation for Sec. Haaland, a member of New Mexico’s Laguna Pueblo tribe and the first Native American presidential cabinet secretary in the U.S.
“The strong return of this treasured bird reminds us of our nation’s shared resilience, and the importance of being responsible stewards of our lands and waters that bind us together,” Haaland said.
The announcement also represented a major advance by the USFWS in using citizen-science powered supercomputing to generate better estimates for the eagle population.
“Working with Cornell to integrate data from our aerial surveys with eBird relative abundance data on Bald Eagles is one of the most impressive ways the we have engaged with citizen science programs to date,” stated USFWS Migratory Birds Program Assistant Director Jerome Ford. “I can honestly say that we would not have the most accurate population estimate available if we did not have the opportunity to work with Cornell. The result of this partnership is the most scientifically robust, thorough population estimate of Bald Eagles in the Lower 48 states, and we look forward to continuing to work with Cornell in the future.”
The new USFWS report estimates 71,467 nesting pairs of Bald Eagles in the Lower 48 states, which is double the number of eagle nests noted in the 2009 report—and many multitudes higher than the all-time recorded low of 417 known eagle nests in 1963. Back then, the popular use of DDT pesticides after World War II had decimated the eagle population. In 1967, the Bald Eagle received protection under the predecessor to the federal Endangered Species Act. Then in 1972, the United States banned DDT.
Thanks to legal protections (the Bald Eagle was a charter member of the eventual ESA signed into law in 1973), captive-breeding programs, and habitat protection around nests, the Bald Eagle population rebounded. From the 1960s through the early 2000s, the USFWS tabulated the growing numbers of eagles through surveys provided from the states. Then in 2009, two years after the Bald Eagle was delisted from the ESA, the agency conducted the first national eagle survey to monitor post-delisting population trends. The 2009 eagle count came from aerial surveys, as pilots from the USFWS Migratory Bird Program flew eagle-counting missions over high-density eagle-nesting areas to count numbers of occupied nests.
For this latest USFWS report, the federal government collaborated with the Cornell Lab to augment their aerial surveys with a big-data population model generated by eBird. The computer science that developed the eBird model was built upon citizen science—more than 180,000 birders who shared data with the Cornell Lab by uploading eBird checklists (tallies of which bird species they saw, and how many, in a single outing). Cornell Lab scientists then developed a model that uses eBird estimates of relative abundance for Bald Eagles to generate numbers of occupied nesting territories in the areas that USFWS was not able to cover in its aerial surveys.
More about eBird Modeling
According to Brian Milsap, national raptor coordinator for the USFWS Division of Migratory Bird Management, the eBird data improved the agency’s estimates, but the overall trend reflects real growth among eagles.
“When we look at the differences between 2009 and now, we believe that by bringing in the eBird data that certainly improved our estimate and probably accounted for more eagles than we were able to account for in 2009,” Milsap said at the press conference. “But if you also look at some other some indices for bird population trends, for example the Breeding Bird Survey, the rate of trend that we see in this survey is pretty comparable to that one.
“The vast majority of this increase really is attributed to Bald Eagle population growth.”
According to Viviana Ruiz-Gutierrez, who supervised the Cornell Lab’s role in the partnership as the Lab’s assistant director of Center for Avian Population Studies, the report marked a milestone for eBird: “One of our main objectives was to see if population modeling based on eBird data would enhance the survey work the Fish and Wildlife Service was already doing. We’re hoping that this will allow the Fish and Wildlife Service to track Bald Eagle populations over a much wider area in the most cost-effective manner in the future.”
At the press conference, Cornell Lab Center for Avian Population Studies Senior Director Amanda Rodewald thanked the USFWS for hosting the event to celebrate eagle recovery, and to celebrate the role of citizen science—the thousands of birders who shared their observations to help build the population models.
“It’s heartening to see how we can all come together in different ways to conserve the birds that we all cherish,” Rodewald said. “We at the Cornell Lab hope that this is just the beginning of many more successful collaborations with the Fish and Wildlife Service.”
All About Birds is a free resource
Available for everyone,
funded by donors like you