The national bird

By BILL CHAISSON
Of a Feather
Last Sunday we were driving from Pawling, N.Y. toward Hartford, Conn. on Interstate 84 when I saw a large hawk-shaped bird wheeling sharply rather low over a field next to the highway. As we drew nearer, the bird got bigger. And bigger. Very quickly it was obvious that it was an adult bald eagle. In the way of all things on an interstate, we were past it in an instant, but it was still a thrilling sight, even though it has become an increasingly common one through my lifetime.

I don’t remember the first time I saw a bald eagle (Haliaeetus leucocephalus), mostly because throughout my teenage years in the 1970s I hoped that every large brown hawk-like object would turn out to be an eagle. It is quite possible I never got a good look at this species until I went to Alaska in 1983. I know I saw several golden eagles in the Plains and mountain states before getting to Seward’s Folly and seeing our resident “fish eagle.”

It is sad to read A.C. Bent’s Life Histories of North American Birds of Prey. This volume of the series was published in 1937, two years before Swiss chemist Paul Hermann Müller discovered the insecticidal properties of dichlorodiphenyltrichloroethane (DDT). After widespread application during World War II, the chemical was made available for use by the public. In 1962 Rachel Carson published Silent Spring, which focused the public attention on the effects of DDT on the environment. Also, by then insects had developed resistance to it. By 1972 its use was banned into the United States.

In the early decades of the 20th century, Bent was blithely unaware of the coming debacle. “My experience with the nesting habits of the bald eagle has been mainly in Florida, where this great bird is widely distributed, very common for a large bird ….” He describes it nesting on golf courses, near houses, and along “much traveled” roads. On the Gulf side of the peninsula it was especially common in Pinellas County (St. Petersburg) and in Brevard County (Cape Canaveral) on the Atlantic.

Because DDT is hydrophobic, it does not dissolve in water and is instead absorbed into organisms. It is lipophilic, so it accumulates in fat deposits, which means that in addition to being found in mother’s milk, it “bioaccumulates” as it passes through the food chain, with predators getting the highest doses. Animals metabolize DDT into DDE (shedding HCl), which in birds interferes with the formation of calcium carbonate and therefore leads to very thin egg shells, especially in birds of prey, waterfowl, and songbirds. In humans it interferes with the reproductive system and is carcinogenic. A worldwide ban was not proposed until 2004 and it is still used widely in India.

DDT was just one of the many challenges faced by the bald eagle population in the “lower 48.” Many other environmental pollutants had various effects, but habitat loss and shooting of the birds made inroads as well. The population below the 40th parallel in the early 18th century is estimated to have been 300,000-500,000. By 1950 there were only 412 nesting pairs in the United States (which did not include Alaska at the time).

According to Bent, bald eagles generally produce only two eggs per brood and some pairs do not breed every year. He described the eggs as “ridiculously small for so large a bird.” Because they are born very small, it takes a long time for nestlings to grow up. After two months in the nest, with both parents bringing them an enormous amount of food, eaglets are fully feathered but their flight feathers are only half-grown.

In 1921 the journal Ecology worried about the possible extirpation of the bald eagle. Writing in 1937, Bent states “The bald eagle probably nested at one time over much of New England, but there are no recent authentic records of its nesting in the three southern states, though it probably still breeds sparingly in the wilder parts of Maine, New Hampshire, and Vermont … Many rumors have come to me of eagles’ nests, and I have spent much time in investigating such reports, but always without success.”

In 1940 Congress passed the Bald Eagle Protection Act (which was expanded in 1962 to include the golden eagle) in the face of steep declines in the population even before the advent of pesticide use. They were widely shot because of exaggerated claims about their predation on fowl and livestock. There was a bounty on them in Alaska (even with few livestock present), so good numbers exist for the number killed: over 100,000 between 1917 and 1953. During this period the human population of the territory increased from 64,000 to 127,000. Even though it was still a territory, not a state, in 1952 Congress extended the rules of the Bald Eagle Protection Act to Alaska.

With the passage of the Endangered Species Act in 1973, the bald eagle was immediately added to the list. In 1995 its status was altered from endangered to threatened. After 1963 buffer zones were widely employed around eagles’ nests to protect them from human activity. In the primary zone (within 1,500 feet) recommended restrictions are extensive. These and other protections, including active reintroduction to some areas via hacking programs, have helped the bald eagle to recover. In 2007 it was no longer considered threatened and was taken off the federal list. In 2017 it was removed from the New Hampshire state list of endangered species.

In 2021 N.H. Audubon counted 81 nesting pairs in the state. In that year my wife and I were living in Sutton. While walking along Newbury Road one day we almost felt the presence of something large in the air — they are 3 feet long with a wingspan up to 8 feet — and we looked up to see a bald eagle cruising south down the Lane River. After all these years they are still breathtaking.