Mistaken Identities: Ospreys vs. Bald Eagles

Birds of a feather flock together ... which is why ospreys and bald eagles don't. But it's easy to confuse these two large birds of prey. Both have sharp eyesight, strong wings and talons, brown and white feathers, and yellow eyes.

They also share a history of population decline. In the 1960s, scientists found that DDT, a synthetic pesticide, made it difficult for ospreys, bald eagles and other raptors to absorb calcium. Because DDT was cheap and initially effective, it was widely used in places like farms, gardens and wetlands. Birds affected by DDT laid eggs with thin shells that often broke before hatching, leading to a decline in their populations. After DDT was banned in the 1970s, osprey and bald eagle numbers both rebounded.

Despite their similar appearances and backgrounds, several key differences set ospreys and bald eagles apart.

Other Differences

Differences in feather color, wings and talons are easy to spot, but they're not the only ways to differentiate between ospreys and bald eagles.

Beaks

Bald eagles' yellow beaks are three times as big as ospreys' smaller black beaks. Ospreys' beaks are also more curved.

Weight

Ospreys weigh about 3.5 to 5 pounds, while bald eagles typically weigh between 8 and 12 pounds.

Diet

While ospreys only eat fish, bald eagles eat fish, carrion, reptiles and other birds (sometimes even ospreys). Bald eagles also commonly "pirate" prey from other birds by forcing them to drop their food mid-flight. When fishing, ospreys often dive into the water to catch prey, while bald eagles snatch fish from the surface of the water.

Nesting

Ospreys engage in colonial nesting, where multiple breeding pairs will nest near each other. These highly adaptable birds are comfortable around humans and prefer to nest on man-made nesting towers, rather than in trees. On the other hand, bald eagles nest alone in trees and are highly territorial. Bald eagles' nests are also bigger, measuring over 6 feet wide, while ospreys' nests are usually under 3 feet wide.

Migration

Some nesting bald eagle pairs don't migrate, while others head south for the winter. All ospreys, though, are migratory and return north between February and April.

Protecting Our Feathered Neighbors

Both ospreys and bald eagles are threatened by habitat loss. To protect bald eagles, people should be especially careful around their nests. Adult eagles may abandon their nests if disturbed. On the other hand, ospreys are less sensitive to humans, but they do depend on fish. Supporting tighter regulations against overfishing will protect ospreys for years to come.

Every year, volunteers from the National Aquarium join Greg Kearns, a naturalist for the Maryland-National Capital Park and Planning Commission, in banding Maryland osprey chicks to track their population. Thanks to years of data, Greg and other experts have seen a recent unprecedented decline in local osprey numbers. While Greg is concerned, he believes that inspiring others to care about this iconic Maryland bird will best safeguard their future.

"I love sharing the wonder and beauty of ospreys with people," Greg said. "I've worked in the field with them for 40 years, and I've handled thousands of ospreys, but I'm constantly amazed by this species. It's an impressive symbol of the Chesapeake Bay."