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All Creatures,

Episode 146: Beauty of Bald Eagles

March 10, 2020

We are back with an American icon, the Bald Eagle. Not only are these incredible raptors, but also a great conservation success story. Once down to a few hundred breeding pairs in the United States (excluding Alaska), their population is back. Each week we learn something new and amazing, and the Bald Eagle is no exception.

Bald Eagle History

The Bald Eagle belongs to the Family Accipitridae. They are a very diverse family of eagles, kites, harriers and vultures. Bald Eagles specifically are also known as “Sea Eagles,” from the genus Haliaeetus. These eagles are spread throughout the world. The scientific name is Haliaeetus leucocephalus. 

Birds evolved over 150 million years ago from the theropod dinosaurs. Sea Eagles are though to have evolved from the kites about 36 million years ago. Bald Eagles specifically can be traced back to a 1 million years ago from fossils found from the La Brea Tar pits in Southern California.

Bald Eagle Physiology

These birds live up to 20 years in the wild, and have been reported to live up to 38 under human care. One report suggests they can live even up to 50. While not the largest birds on Earth, they do have a wingspan of nearly 7 feet 7 inches (2.3 meters). Interestingly, the females are about 25% larger than the males. These birds have incredible eye sight, and are thought to be able to see objects 4x greater than the human eye.

The bald eagle primarily feeds on fish, especially ones small in size that they can swallow whole. They will also eat small mammals, small birds, injured waterfowl, and carrion when abundance of fish is not available. One study found fish comprised 56% of the diet of eagles, birds 28%, mammals 14% and other prey 2%, Other studies show fish make up 90% of diet. It has also been reported rather than do their own fishing, Bald Eagles often go after other creatures’ catches. It has been observed that a Bald Eagle will harass a hunting Osprey until the smaller raptor drops its prey in midair, where the eagle swoops it up. A Bald Eagle may even snatch a fish directly out of an Osprey’s talons.

Bald Eagle Conservation

Bald Eagles in the 19th century were estimated to be 300,000 up to 500,000 strong. Their populations plummeted in the 20th century, hunted and persecuted by humans. Protections were introduced but the use of DDT hit them even harder. It was not until the full ban of DDT did the Bald Eagle truly start to thrive. Today there are an estimated 300,000 adults and are listed as Least Concern by the IUCN

Video

Bald Eagle Courtship

Conservation Organization

American Bird Conservancy 

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