Wild Relatives: The bone-eating bearded vulture

Editor’s note: Our Wild Relatives story series will explore the connections between our local wildlife species and related animals from around the globe. By learning about these exotic species, we hope to foster appreciation for the remarkable creatures that live in our backyards and neighborhoods.

Vultures are birds that are most known for their unique appearance and their unique diet. These large birds won't win any beauty contests, and their steady diet of animal carcasses isn't very common in the animal kingdom.

A bearded vulture. (Photo via Adobe Stock)

There's one vulture species, called the the bearded vulture, that takes things a bit farther on the food front. Like other vultures, bearded vultures primarily eat dead animals, but there's one part of the carcass they are especially interested in — the bones. That's right, these vultures primarily eat bones!

A bony diet

Eating mostly bones might seem like an odd choice, and it is. Bearded vultures are the only bird in the world that mostly eats bones. They have a very acidic digestive system that breaks down the bony material so the birds can benefit from the fat and nutrients inside.

Bearded vultures, which are also called lammergeiers, often eat bones of very large animals, including deer, cattle and sheep. They can pick up bones more than a foot long and then fly up into the sky before dropping the bones to the ground below. This causes the bones to break into smaller pieces, which makes them easier for the birds to eat.

While the vultures primarily feast on dead animals, they can hunt live animals. When they do, they rely on the same technique of lifting their catch up into the air and allowing it to drop down to make it easier to eat. About 85% of an adult bearded vulture's diet consists of bones, but the chicks eat more flesh and meat as they mature and grow.

Old World vs. New World vultures

Bearded vultures are related to the turkey vultures that we see soaring overhead here in Illinois, but they are classified as a different type of vulture. Turkey vultures are New World vultures. They are characterized by their bald heads. Bearded vultures are Old World vultures, and these birds don't have bald heads. Instead, they look more like some of their raptor relatives, including eagles and hawks.

New World vultures are found in North America, South America and Central America, while Old World vultures live in Africa, Asia and Europe. Another difference between the two families of vultures is how they vocalize. New World vultures can hiss and grunt, but they don't otherwise make much noise. But bearded vultures can be loud. Sometimes they even scream in flight while trying to attract a mating partner.

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Words to know

Carcass: The dead body of an animal.

Characterize: To be typical or characteristic of.

Intimidate: To frighten something or someone to make them do what one wants.

Primarily: For the most part.

Rugged: Having a broken, rocky or uneven surface.

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Even without bald heads, bearded vultures are an unusual looking bird, and it's partly by choice. These large birds have dark wings and backs and stringy beards for which they are named. Another unique feature is that their heads, chests and legs are often a reddish orange color that they dye themselves. They acquire this reddish color by bathing themselves in rusty water or red soil. If not for their dye jobs, these reddish parts would be white.

They are the only birds in the world known to change their color intentionally, but the reason they dye their feathers isn't entirely understood. Some believe they coat their feathers in iron oxide, which is where the color comes from, as a way to kill microbes. Another theory is that the bright color is meant to signal the birds' health and fitness to other birds and to intimidate other vultures.

As is the case with many raptors, female bearded vultures are larger than males. The birds can weigh between 9 pounds and 15 pounds and have wingspans of between 8 feet and 9 1/2 feet.

Mountain birds

Bearded vultures typically live across mountain ranges in Africa, Asia and Europe. They most often choose to live in rugged remote areas that overlook meadows where they may find animal carcasses to feed on.

Bearded vultures do not reach maturity until they are between 5 and 7 years old and may not begin breeding until they are 8. A pair of bearded vultures will typically mate for life. Sometimes, they will join together in groups of three, with an unattached male joining a male and female pair. They can have multiple nest locations across their range, moving between them from year to year.

These birds are the rarest vulture species across Europe. Their population dropped significantly in the 19th and 20th centuries, when the birds were persecuted and also suffered losses due to changes in land use and agricultural practices.

Today, their population is increasing across Europe thanks to successful conservation efforts, and they can again be seen in mountain ranges where they were once absent. Across their entire range, the population is decreasing. They are classified as near threatened on the IUCN Red List of Threatened Species.