Bearded Vulture Nests Hold Trove Of Centuries-Old Artifacts

Picking through a dozen vulture nests, scientists discovered hundreds of artifacts, including a sandal that could be more than 700 years old.

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:01Flora Lichtman?

  Hey, it's Flora Lichtman and you're listening to Science Friday.

• 0:07Flora Lichtman?

  Today on the podcast, bone-eating vultures that are stashing some surprises in their nests.

• 0:15Speaker 01

  So we were expecting to find bones and a stick, which is the main element of the nest. But who would be expecting to find an 800-year-old shoe? Nobody.

• 0:32Flora Lichtman?

  The bearded vulture is the only animal on Earth whose main diet is bones, and one of the very few to successfully rock a soul patch. But apparently, these vultures aren't just scavenging skeletons. They've been stashing human artifacts in their nests for hundreds of years. Reporting in the journal Ecology, scientists picked apart 12 preserved vulture nests and found a museum collection, hundreds of ancient artifacts, including a woven sandal that could be more than 700 years old. The nests aren't just giving us a glimpse into vulture culture, but also the lives of the people they lived beside. Here to dissect the findings is the study author,

• 1:16Flora Lichtman?

  Dr. Ana Belén Marine Orojo, an archaeologist studying ancient human diets at the University of Cantabria in Spain. Ana, welcome to Science Friday.

• 1:25Speaker 01

  Oh, hello. How are you doing?

• 1:27Flora Lichtman?

  I'm great. You know, finding a 700-year-old shoe in a nest seems really surprising to me. But what was it like for you? Were you expecting to find these artifacts?

• 1:41Speaker 01

  Not at all. It was even more surprising for us.

• 1:45Flora Lichtman?

  Really?

• 1:46Speaker 01

  Yes, because we didn't expect it when we were investigating the diet of this bearded vulture. So we were expecting to find bones and a stick, which is the main element of the nest. But who would be expecting to find an 800-year-old shoe? Nobody.

• 2:07Flora Lichtman?

  Give us a sense, what do these birds look like?

• 2:10Speaker 01

  Oh, it's lovely. I mean, it's really nice and really majestic, I will say. Because it can be when the wings are fully open, it can reach a 2.4 meters wide. It has a very beautiful orange color. This is very nice. This is very beautiful, the orange color they have in contrast with the black wings.

• 2:40Flora Lichtman?

  How big are these nests?

• 2:42Speaker 01

  They are quite massive, so I will say, um, so 1.5 meters wide. And it has been accumulated through time. Some of them, they were in deep, like four meters.

• 2:58Flora Lichtman?

  Wow, okay, so that's like about five feet wide and then, and they can be four, did you say four meters deep? That's like, that's like over 10 feet deep.

• 3:10Speaker 01

  Yes, they are quite deep and they have been used through centuries by the Bearded vulture.

• 3:17Flora Lichtman?

  Wow, okay, so the nests were in use for hundreds of years by vultures?

• 3:21Speaker 01

  Yes, that's right. We consider that this nest has been accumulated for several centuries. This is what we didn't know. We knew that these were historical nests, that the Bearded vulture left empty or non-used for the last 100 years because the species has disappeared in this part of Spain. But we didn't know for how many years the Bearded vulture have been nesting in the same places over and over and over. So, no, it wasn't until we dated by carbon 14.

• 4:07Speaker 01

  And the most surprising discovery was to find these shoes made on grass that someone used almost 800 years ago. And there are different shoes with different techniques and they are really, really amazing.

• 4:24Flora Lichtman?

  What were some of the other finds? What were the best nest finds?

• 4:29Speaker 01

  Well, we accessed 12 nests. What is the most abundant element in the nest? Sticks, bones, also eggshells, fragments. And the surprising thing for us was to start recovering these ethnographic elements like shoes, baskets made with grasses. And also, we found an arrow with a metal point. Also, we found a leather mask painted with red lines. And we didn't know which kind of animal's leather was.

• 5:14Speaker 01

  So we achieved a proteomic analysis that gave us the result that this leather mask was made on a sheep.

• 5:25Flora Lichtman?

  Wow, sheep leather. So it gives you a sense of sort of what the people were doing who were living, you know, at the same time as these vultures.

• 5:33Speaker 01

  Yeah, all the material that has been recovered in the nest provide us with various information. So like, what kind of trees were in the environment?

• 5:44Flora Lichtman?

  Right.

• 5:44Speaker 01

  They were used by the bird vulture to make their nest. What kind of animals were living in the landscape? The eggshells we are planning to analyze will provide us with information about if there was contaminant in the environment. So we will know if there was lead used by hunters in the environment at that time. And obviously, the most interesting thing for us and the most surprising thing is all these various different shoes with different techniques made on grass.

• 6:23Flora Lichtman?

  Yeah, I have to ask about the shoes. Why are birds using these artifacts in their nests? Like, why is it helpful to have a shoe in your nest?

• 6:32Speaker 01

  This is a very good question. So in order to thermoregulate the temperature in the nest when they put the egg is to bring...

• 6:44Speaker 01

  Ah, material to keep warm the, the nest. But in this case, the bird found these shoes probably abandoned in the nature. And consider, um, this will be very good to thermal regulate the temperature because it's uh thick and um stable and I will take it to my nest. So we found these different shoes in different nests, uh in different layers. And uh we dated some of them. And one of the shoes uh were from the 13th century. So this means they have uh almost eight hundred years ago.

• 7:25Flora Lichtman?

  Yeah, wow, eight hundred years, yeah.

• 7:27Speaker 01

  Yeah, and we uh dated also uh the fragment of the um grass basket, basket. And this is more recent, this is from the eighteenth century. But here, the most interesting thing is what is coming. Because we have so many shoes to date, we have so many material to analyze that this can still provide us in the future with even more uh great surprises.

• 7:59Flora Lichtman?

  We've been talking about their nest building, but we, we need to spend a moment on their diet. How do they survive on bones?

• 8:08Speaker 01

  Well, this is the most surprising thing of this Bearded vulture. Seventy, eighty percent of the diet are composed of bones. This uh animal is the last one in the trophy chain. So he doesn't compete with other carnivores or other vultures for uh getting uh access to the uh carri- caronia, car- carrion. So the flesh of the uh animal carcasses. No, he's uh, we have, we have videos of him, of his behavior and he's just waiting for the others to finish. And.

• 8:48Speaker 01

  When the others have finished, so he doesn't really compete or fight for for food. He eats the uh he select the bones. And we see that he has a preference for the distal part of the legs, basically the metapodiums and the phalanges. Because uh these bones has the highest uh grease content.

• 9:12Flora Lichtman?

  Grease content?

• 9:13Speaker 01

  On the animal skeleton. So he usually select herbivores skeletons, okay, so like sheep, goat, um deers. Uh this is what the animals they they eat, herbivores. So um what he does is very curious. So he's flying, imagine he's flying on the nature and suddenly he saw a carcass of an skeleton of an animal. So he selected the long bones usually. And what he does is going up up to seven to eighty meters and then drop the bone.

• 9:52Speaker 01

  On the mountain, on an area where there are stones in order that the impact of the um of the bone on the stones. Break the bones.

• 10:04Flora Lichtman?

  Like seagulls with muscle shells.

• 10:06Speaker 01

  Yes, so in this way, he has this long bone in a small pieces, which is easier easier for him. To swallow.

• 10:17Flora Lichtman?

  Doesn't seem that easy, though, even in small pieces.

• 10:21Speaker 01

  Well, but he this is his behavior and how he uh understand that in that way can eat. More easily the bones. And his uh pH is so low. That he has the capacity of uh digested the bones. Because neither of us will even hyenas could really digest the bones, but he does.

• 10:52Flora Lichtman?

  The stomach acid just melts those bones.

• 10:55Speaker 01

  Totally melted and when we see his uh feces, they are chalk.

• 11:01Flora Lichtman?

  Chalk, wow.

• 11:04Flora Lichtman?

  You know, you write that these birds, the bearded vulture nests are natural museums. Tell me about that idea.

• 11:10Speaker 01

  Well, it's because otherwise we wouldn't have recovered these human-made artifacts. And it's opening us a new line of research to investigate all the different vegetable materials, the different grasses to make these shoes, to make this basket. So we are planning now to investigate the different techniques used for these humans through time. And obviously, we need to date it, everything, in order to know for how long this nest has been occupied.

• 11:53Flora Lichtman?

  I can't wait to find out.

• 11:54Speaker 01

  Yeah, me too. I mean, I'm just looking forward to get the funding, to send the samples for dating and hear from the results, because I think that it's gonna be really, really cool.

• 12:09Flora Lichtman?

  Well, good luck. Study author Dr. Ana Belén Marine Arroyo, an archaeologist and professor at the University of Cantabria in Spain. Ana, thank you so much for joining me today.

• 12:18Speaker 01

  Thank you very much for your interest, and it was a pleasure.

• 12:27Flora Lichtman?

  Today's episode was produced by Rasha Aridi.

• 12:31Flora Lichtman?

  I'm Flora Lichtman. Thanks for listening.