Bald Eagle Size, Diet and History as a National Icon

Female bald eagles are larger than males, and can weigh anywhere from 10 to 14 pounds (4.5 to 6.3 kilograms). Her wingspan will be between 6 to 7 feet (1.8 to 2.1 meters) The male bald eagle is smaller, at around 9 to 10 pounds (4 to 4.5 kilograms). His wingspan is about 5.5 to 6 feet (1.6 to 1.8 meters).

While the bald eagle's size is indeed impressive, they aren't the only North American bird with an impressive wingspan. The golden eagle, for example, is commonly measured as being about on par with the bald eagle's wingspan, at about 6 to 7 feet (1.8 to 2.1 meters).

The California condor, on the other hand, easily bests the bald eagle in terms of wingspan. Adult specimens can easily reach 9 to 10 feet (2.7 to 3 meters).

The adult bald eagle doesn't have the "bald" moniker because his scalp looks hairless, but because it's white. Its name comes from the Middle English word "balde" which means "white."

In fact, adult bald eagles don't even develop their striking white head and tail feathers until they are mature, somewhere between 4 and 5 years old.

The young birds don't usually attain adult plumage until their fifth year. Instead of the adult bald eagle's white head and neck, the immature bald eagles are mostly dark brown, with mottled brown and white wings.

So, what else do bald eagles eat? Mostly fish, waterfowl and other small game like rabbits, squirrels or rodents. They require a pretty wide hunting territory, about 25 miles (40 kilometers). A 6-pound (2.7 kilogram) eagle (which is about average) can live off two adult rats easily.

"That's a daily feed," says Courdin. "But most birds don't eat every day because they will catch something that's large enough to sustain them for a couple of days. Instead, they might feed off something large and fill their crop, a part of their digestive system where they temporarily store food that can sustain them for two or three days. Sometimes even longer."

Since they are a type of sea eagle, this preponderance of fish in the bald eagle's diet is easy to understand.

Bald eagles are considered opportunistic carnivores, which means that they usually eat whatever is available. That includes dead fish that have washed up on shore, or even stealing from other birds such as ospreys.

This type of food-snatching behavior has a specific name, and not a very nice one: "kleptoparasitism." But it's more common among the immature birds. Once mature, bald eagles can be formidable hunters when necessary. When a bald eagle swoops down to catch its prey, it uses its razor-sharp talons to snatch the unlucky animal it has decided to make a meal out of.

Bald eagles are the only sea eagles endemic to North America, and they really have the territory covered. The bald eagle's range stretches from Southern Alaska to Northern Mexico, and from coast to coast.

Due to their distinctive plumage, they are almost impossible to mistake with other birds, even other large eagles.

Therefore, unlike other raptors (such as the red-tailed hawk), you don't have to consider whether you're looking at a bald eagle, a white-tailed eagle, Steller's sea eagle or any of the other largest eagles in the world. When you see that white head soaring above the trees, it's a bald eagle for sure.

Bald eagles mate for life. If one mate dies, the remaining bird may take a new mate. Mates build nests, or aeries, together, which takes about one to three months. They also trade parental duties, with each adult bird taking their turn sitting on the eggs (although the females tend to do this more).

Because it takes 10 to 12 weeks for eagles to grow and fledge (take their first flight), eagles lay only one clutch (or group of eggs) per year. Both parents share incubation duties (35 days).

"If their eggs or their young are destroyed early enough in the season, they will lay another clutch to try to reproduce again," Courdin says. "In fact, that's part of how they got the (bald) eagle population back up. They would remove eagle eggs from the nest early in the season and the adult eagle would lay another set of eggs. It's called a 'double clutch.'"

Bald eagles have the largest nest of any bird species in North America.The average nest size is 4 to 5 feet (1.2 to 1.5 meters) in diameter and 2 to 4 feet (0.5 to 1.2 meters) deep. The biggest aerie on record was built by a pair of bald eagles in St. Petersburg, Florida. It was 9 feet (2.9 meters) wide, 20 feet (6 meters) deep and weighed 2 tons (1.8 metric tons).

"Eagles only live in their nest during the mating season, incubation and while they're raising the fledglings," says Courdin. "Once they learn to fly and everyone is out, they don't live in the nest."

These nest-building champs return to the same nest year after year, if possible, but will leave if the tree it's built in can't sustain it.

Courdin has worked with many raptors but says bald eagles are unique.

"They tend to never forget anything and they hold grudges," he adds. "If you're training an eagle and you make a mistake, that can either ruin the training you've done or set you back several months." Courdin said it took five years to train Freedom, the male bald eagle trained at the Raptor Center.

Believe it or not, Founding Father Benjamin Franklin favored the turkey as the national bird, instead of the bald eagle, calling it more "respectable," and "withal a true, original native of America."

Courdin says part of Franklin's beef was that the bald eagle is a scavenger. "Which they are," he adds. "Of all the birds of prey other than vultures, bald eagles will most readily go to a dead animal on the side of the road where other birds of prey will only eat carrion if they are starving."

Nevertheless, the bald eagle was chosen as a symbol of strength, courage and freedom. And despite Franklin's comments, the bald eagle is indigenous only to North America (unlike other eagle species).