DOVER — Delaware’s bald eagle population has risen considerably in recent years, and is expected to continue to increase, according to the Delaware Department of Natural Resources & Environmental Control.

Jordan Brown is an avian biologist who runs research on non-game land bird species for the state’s Division of Fish & Wildlife. According to Ms. Brown, the birds, which are native to the First State and have been the national bird since 1782, have a much healthier population today than they did just a few decades ago.

“We’re now doing aerial surveys by plane every five years, and each year that we do this, we end up with more nests than in previous years. So, the number is definitely going up,” said Ms. Brown. “The last one was in 2018, and there were 132 nests observed, and there were at least 77 active breeding pairs, which is great. Back in 2014, we had about 54 active breeding pairs.”

The Delaware River Basin Commission, a federal and interstate agency that protects and ensures fair usage of the Delaware River, notes on their website that in the 1980s “there were as few as two to four nesting pairs in the entire state” of Delaware.

Bald eagles faced serious danger of extinction starting in the mid-20th century due to several irresponsible farming and hunting practices, according to the U.S. Fish & Wildlife Service.

“In the mid-1900s, our national symbol was in danger of extinction throughout most of its range. Habitat destruction and degradation, illegal shooting, and the contamination of its food source, largely as a consequence of DDT, decimated the eagle population,” says the national agency’s website.

Dichlorodiphenyltrichloroethane, commonly referred to as DDT, is a harmful pesticide that was used widely starting in the 1940s and ’50s that posed a lethal danger to bald eagle populations by weakening their reproductive abilities.

However, following the passage of the Endangered Species Act and a national ban on DDT in the early 1970s, bald eagle populations slowly and surely began to rebound across the country. In 2007, they were removed from the endangered species list.

However, Ms. Brown noted that they are still protected by legislation on both the state and federal level. National laws such as Migratory Bird Treaty Act and Bald and Gold Eagle Protection Act are in place to protect bald eagle populations across the country. They are additionally classified as a species of greatest conservation need in Delaware state law.

Ms. Brown said that this classification “indicates that there are some research and conservation needs for the species, but they are not endangered.”

In addition to their purpose as a national symbol, bald eagles serve an important role as an environmental indicator because they sit at the top of the food chain. Accordingly, they could provide a strong signal of the impacts of climate change and future pollution in the state.

“They are beautiful birds, and the fact that they consume mammals and fish does give us an idea of how our ecosystem is doing. They can be an indicator species for things like disease, or poisons, different rodenticides, and contaminants. They can alert us of issues in the ecosystem,” said Ms. Brown.

Indicators include a large increase or decrease in population, testing blood samples and carcasses that the birds have fed on for contaminants, amongst others.

“If any of those things come back positive for contaminants, or if there have been large outbreaks of birds dying, typically like vultures and bald eagles in a particular area, it might indicate to us that there has been a poisoning in that specific area that needs to be investigated,” she said.

Delaware residents who observe bald eagles near their homes need not be concerned for themselves or their small pets, according to Ms. Brown. Instead, she says they should appreciate what their presence represents.

“I don’t particularly think that there is any reason to be worried, and I think that people should just feel excited that the eagle has chosen their area,” she said. “That means that they live in a good ecosystem where there’s plenty of food.”

Bald eagle populations are expected to increase, or at least remain stable, if environmental conditions remain the same. Climate change and pollution could pose a threat in the future, but Ms. Brown said, “there’s no way to exactly predict how it would affect eagles.”

Local residents who observe and photograph eagles and want to contribute to data collection on the species can find instructions on the Delaware Division of Fish & Wildlife’s website.