Nature Notes: Bald Eagle
As a young man just out of college, I was thrilled by my maiden visit to the Rockies for a backpacking trip in Montana’s stunning Glacier National Park. On our third day in remote country, we hiked to a large lake and rested along the shore. Suddenly overhead we spotted a huge, dark bird with a white head and tail; my first bald eagle. I’ll never forget those minutes watching the magnificent bird gliding on afternoon thermals above the water. Despite living in Harpswell for eight years, I still get a rush when I see the big eagles in the sky above our town.
There is no doubt that bald eagles are memorable, partly because they are one of the largest birds in North America. An adult female, larger than the male, may reach three feet in length, with a wing span that stretches beyond seven feet. In Alaska, a rich diet of salmon allows some females to exceed 15 pounds, making them a formidable predator. Thanks to their over-sized strong wings, bald eagles have been documented lifting and flying away with deer fawns and fish up to their own weight. They can even snag sizable fish out of the water and take flight back to their perch for feeding.
Bald eagles also capture our attention with their appearance. While juvenile eagles can look rather scruffy as their adult feathers are growing in, the adults are striking birds. Their bodies are predominantly blackish brown, making a distinctive contrast with the bright white head, neck and tail feathers. Their feet and bills are yellow, and those piercing eyes, almost as large as our own, are a stark yellow. Throw in sharp talons 10 times more powerful than human hands, and a hooked beak for tearing food, and this bird is every bit a fierce competitor in a tough world.
Yet we nearly lost these eagles in the last century. From a population estimated up to 500,000 in the early 1800s, the population had fallen to just over 400 breeding pairs by the 1950s. Loss of habitat, pollution, unrestricted hunting and the pesticide DDT made life very tough for bald eagles until new laws were passed. First the 1918 Migratory Bird Treaty, and then the Bald and Golden Eagle Protection Act of 1940, limited the effects of human hunters. In 1967, the bald eagle was declared an endangered species, and finally DDT was banned in 1972. Fortunately, the bald eagle has made a huge recovery with their population now estimated at 70,000-90,000, with 50 percent in Alaska, 20-30 percent in British Columbia and more than 10,000 mating pairs in the lower 48 states.
It takes four to five years for a bald eagle to reach maturity. Although the birds are solitary during the fall and winter months, eagles mate for life, and breeding takes place quite early in the season. Eagle nests are amazing constructions, generally found high in huge old trees, and often used for years on end. The largest nest on record was more than 12 feet tall, eight feet wide and estimated to weigh more than one ton! The female lays two to three eggs and incubates them just over one month, with the hatch taking place in April or May. Both parents are engaged in feeding the chicks. Fledgling normally occurs in 10-12 weeks. Their life span in the wild is ranges from 15 to 30 years.
To understand the feeding preferences of bald eagles, we can look to its scientific name, Haliaeetus leucocephalus. The Greek root words tell us this is a sea eagle with a white head. Depending upon the location of the nest, the eagle diet may be up to 80 percent fish. Other favored prey include water birds such as ducks and gulls, rabbits, raccoons, snakes, muskrats and turtles. The eagle is quite happy to eat carrion if that is the easiest meal on offer, and is not above stealing food from smaller competitors. It takes a lot of food to keep an eagle going – scientists have measured their resting heart rate between 100-120 beats per minute, and their body temperature exceeds 105 degrees Fahrenheit. In winter, I have watched eagles in Reed Cove diving at sea gulls, and they sometimes clean up fish carcasses that wash up on the beach.
The bald eagle is capable of speeds more than 40 mph with good thermals, and its diagonal dive speed can nearly hit 100 mph. Imagine seeing one of them approaching at that speed with wings spread and talons arched toward a target!
The bald eagle is revered in many Native American cultures, and feathers or claws have long been used in their rituals. The bird is sacred and considered by some tribes as a spiritual messenger between the gods and humans. Current federal law limits the possession of eagle parts only to certain Native Americans. The fines for breaking this law can be stiff, so if you find an eagle carcass or feathers, either leave them where you found them or report them to the authorities.
Habitat is critical for the ongoing success of bald eagles, especially when they live in areas like Harpswell that are increasingly favored for human use. Eagles favor sites with easy access to large bodies of water such as fresh water lakes, major rivers or areas like Middle Bay and Long Reach. They need the security of forest cover and minimal human disturbance, ideally at least half a mile from active human residences. During the nesting period, eagles are very sensitive to disruptions or threats and may leave the nest in the face of repeated events. This species is one of the most visible that will benefit from permanent protection of the Otter Brook area, since eagles are known to nest regularly in the area along this vital wildlife corridor. For more on Otter Brook, click here.
Like the Roman emperors before them, the founding fathers of America chose eagle imagery for the official government seals and banners. In 1782, the new Congress adopted the Great Seal of the United States with a bald eagle clutching an olive branch and 13 arrows (one for each state). Today we still use the eagle on our coinage. We are told that the great Ben Franklin took issue with the choice of the bald eagle, favoring instead the wild turkey. Franklin viewed the eagle as a coward and a bully, and felt the turkey was a more worthy representative of our nation’s ideals. In this case, I have to disagree with Old Ben. The bald eagle was chosen as a symbol of strength, courage and freedom for a new country escaping from tyranny. As much as I admire the wild turkey, I don’t think its image would have conveyed the right kind of message to those who sought to suppress our new nation.
With luck and care on our part, the bald eagle will long take flight over the waters of Harpswell. We can help them along by protecting critical habitat areas, forever.