Last week was International Vulture Awareness Day! And what better way to celebrate than taking a closer look at the prettiest vulture around: the bearded vulture.
Bearded vultures (Gypateus barbatus), also known as lammergeiers, are scavenger birds found across southern Europe and Asia. Their typical habitat is at high elevations in mountainous regions; most often, you’ll find bearded vultures in areas with cliffs and gorges where they can overlook their prey.
These birds are large and are considered to be the largest Old World vultures around. A large bearded vulture weighs more than my cat, with the species typically weighing between 9.9 and 15.8 pounds (4.5 to 7.2 kg). This heavy weight (for a bird) comes with an impressive wingspan between 90.9 and 111.4 inches (231 to 283 cm).
Beautiful feathers
Bearded vultures have a unique look for a vulture. Unlike other vultures with featherless heads, bearded vultures have a head full of feathers. In fact, they get their name from the long, black bristles that hang down the side of their beak like a beard.
Most vultures have a bald head for an excellent reason: their food. Eating dead, rotting flesh makes it challenging to keep feathers clean! So, how do bearded vultures get away with a feathered head? They eat a much less messy and bloody food: bones.
Bone crushers
Like other vultures, bearded vultures are scavengers. But unlike other vultures, they don’t typically eat dead meat. Instead, bearded vultures are the only birds that almost exclusively feed on bones, making up 85 – 90% of their diet. Bearded vultures are often the last ones to arrive at a carcass, preferring to let other scavengers pick the bones clean before they dig in themselves.
Bearded vultures can eat bones partly because of their strong stomach acid. Their stomach acid has a pH of less than 1, about 100 times more concentrated than human stomach acid. This lets bearded vultures digest entire bones in less than 24 hours!
But to eat a bone, it has to first fit in your mouth. While bearded vultures can eat pretty large bones (up to 10 cm in diameter), they deal with larger ones by breaking them. After picking up a large bone in their talons, bearded vultures carry it to a rocky bone-dropping site called an ‘ossuary.’ Here, the bone is dropped repeatedly until broken open, and the marrow can be eaten. Bearded vultures sometimes use this technique with smaller animals like tortoises and small birds.
However, bearded vultures aren’t born as exclusive bone eaters. Chicks must eat meat and skin, transitioning to bones as they age. And unlike other vultures, who regurgitate their food for their young, bearded vultures deliver whole scraps of meat for dinner.
Bearded vulture chicks will also eat their siblings. Clutches only contain one to two eggs, which hatch around six days apart. The first chick to hatch is usually larger and stronger than its younger sibling, and its parents will preferentially feed their oldest chick. The younger chick usually dies quickly after hatching, and its remains are fed to the survivor.
Why bother having more than one egg if you’re only going to feed one chick? Because you always need backup children! The younger chicks are thought to serve as insurance in case the first chick does not survive.
Dressing up
In addition to their unique diet, bearded vultures are special because they are one of the only birds to use ‘cosmetics’ and decorate themselves. When given a chance, bearded vultures will roll in soil or water rich in iron oxide deposits, turning their typically white feathers red.
This behavior doesn’t seem to be an accident or the result of birds randomly standing near iron deposits. Captive bearded vultures will also decorate themselves, suggesting it’s innate. And the birds will even use their beaks and talons to rub the color around their body!
So why do bearded vultures paint themselves red? There are two competing hypotheses. One is that it serves as an antibacterial wash. Adding strength to this argument is that bearded vultures will rub their freshly painted feathers on their eggs and offspring, potentially giving them a ‘bath.’ But the issue with this prophylactic hypothesis is that iron oxides don’t seem to kill bacteria!
The other popular hypothesis for why bearded vultures paint themselves is that it serves as a signal of strength and dominance. It’s relatively rare to find a suitable iron oxide deposit in the wild; they take time and energy to discover, things that only a healthy, strong bird could really afford to do. In addition, older, larger, and more dominant birds typically have more intense red coloring, further suggesting that being red is a sign of strength and ability.
Not dangerous
Unfortunately, bearded vultures have had a less-than-stellar reputation in the past. The name ‘lammergeier’ is German for ‘lamb vulture’ – people assumed that bearded vultures would kill lambs and even small children for food. This is, of course, a myth! Bearded vultures are scavengers and typically only eat dead animals (and their bones). Most living animals have nothing to fear from these large birds.
However, there is one story of a bearded vulture killing a human. Once upon a time, the ancient Greek playwright Aeschylus received a prophecy warning him of falling objects. So, like any reasonable person would do, he started spending most of his time outside. Unfortunately, a large bird thought his shiny, bald head was a rock and dropped a turtle on it, killing Aeschylus instantly.
Now, this story may or may not be true. But either way, it doesn’t hurt to be careful if you’re hiking in the Alps!
Resources
Leave a Reply