Sabrina Xie/Sun Graphic Designer

May 3, 2021

Local Birders Record Rise in Bald Eagle Populations with Cornell App

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According to the U.S. Fish and Wildlife Service, the american bald eagle population has quadrupled in the last 12 years —  eBird, a Cornell Lab of Ornithology app and database, played a significant role in chronicling this resurgence. Nonetheless, the bald eagle population remains under close monitoring by the U.S. Fish and Wildlife Service.

eBird — a database available to the public for tracking bird sightings and sharing bird-related information — provides policy makers documentation of bird distribution and habitat use to help explain the decrease in certain bird populations, explained Viviana Ruiz Gutierrez, a quantitative ecologist for the Cornell Lab of Ornithology. 

The predictions  informed by eBird aim to confirm the U.S. Fish and Wildlife Service’s population survey results, which provide information about bald eagle populations’ abundance, distribution and trends. According to Ruiz Gutierrez, the eBird data allows for much more precise estimates. 

Ruiz Gutierrez said that bald eagle population growth will likely continue. However, this growth is not uniform across the U.S.. According to Ruiz Gutierrez, refining population size estimates is one of the next steps towards taking this into consideration. 

Refining the areas for population estimates can help to narrow down factors that contribute to a declining population. 

“Where they are declining, we can start asking ourselves why they’re declining. We can also make sure that all of the factors that have contributed to the population increases are still continuing, so that they can help the population increase in most of the U.S.,” Ruiz Gutierrez said. 

The rise of the bald eagle population is promising for the future of North American ecosystems, Ruiz Gutierrez said. 

Ruiz Gutierrez said that bird populations can indicate healthy and functional ecosystems because they are at the top of their ecosystem’s food chain — a rise in bald eagle population leads to more energy flow which maintains the structure of their ecosystem’s food chain.

“Birds are our sentinels of how the environment is doing — they are our canaries of the health of our ecosystems,” Ruiz Gutierrez said. “They provide many ecosystem services, like pest control and seed dispersal, that are important in our day to day lives but also for other areas such as food production.”

Historically, the bald eagle population has been low due to usage of pesticides such as dichlorodiphenyltrichloroethane, which weakens bird eggshells. 

In the United States, bald eagle habitats which include estuaries, lakes, reservoirs, rivers and sea coasts in Alaska, the Great Lakes states, Florida, the Pacific Northwest, the Greater Yellowstone area and the Chesapeake Bay region have been destruction and degradation

Ruiz Gutierrez explained that protections and habitat restoration efforts have contributed to the bald eagles’ rising population. Eagle nesting areas are one specific example of this. These nesting areas are in trees that are close to bodies of water. Bald eagles are protected by the Bald and Golden Eagle Protection Act and Migratory Bird Treaty Act

“There really has been a whole lot of contributing factors, but mainly very targeted efforts to know where bald eagles are, what they need to succeed there, and really investing in these efforts from state to state and at the federal level,” Ruiz Gutierrez said. 

Along with their environmental importance, bald eagles hold powerful symbolic value. For example, eagles are one of the most common clan animals — the Chippewa, the Hopi and the Zuni are some tribes with Eagle Clans. 

“Bald eagles are specifically important — they are America’s national symbol, but also considered as a sacred species to American Indian people,” Ruiz Gutierrez said. 

U.S. Fish and Wildlife Service surveys and the Cornell Lab of Ornithology’s eBird data has been crucial in tracking their population trends.

“None of this would be possible without the contributions of over 180,000 birders who have submitted observations in the US,” Ruiz Gutierrez said.