Science Friday - Bearded Vulture Nests Hold Trove Of Centuries-Old Artifacts

Episode Date: November 13, 2025

Bearded vultures build giant, elaborate nests that are passed down from generation to generation. And according to a new study, some of these scavengers have collected bits and bobs of human history over the course of centuries. Scientists picked apart 12 vulture nests preserved in Spain and discovered a museum collection’s worth of objects, including a woven sandal that could be more than 700 years old.  Host Flora Lichtman talks with study author Ana Belen Marín-Arroyo, an archaeologist who studies ancient humans, about how the nests are giving us a glimpse into vulture culture as well as the lives of the people they lived beside.Guest: Dr. Ana Belen Marín-Arroyo is an archeologist and professor of prehistory at the University of Cantabria in Spain.Transcripts for each episode are available within 1-3 days at sciencefriday.com.  Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

Hey, it's Flora Lichten, and you're listening to Science Friday. Today on the podcast, bone-eating vultures that are stashing some surprises in their nests. So we were expecting to find bones and stick, which is the main element of the nest. But who would be expecting to find an 800-year-shed? Nobody. The bearded vulture is the only animal on earth whose main diet. it 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, Dr. Anna Belen-Marine Oroyo, and archaeologists studying ancient human diets at the University of Cantabria in Spain. Anna, welcome to Science Friday. Oh, hello. How are you doing? 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? Not at all. It was even more surprising for us. Really? Yes, because we didn't expect it when we were investigated the die of this birded boulchur.

So we were expecting to find bones and stick, which is the main element of the nest. But who would be expecting to find an 800-year-shed? Nobody. Give us a sense. What do these birds look like? Oh, it's lovely. I mean, it's really nice and really majestic, I will say, because it can be when the winds are fully open, it can reach 2.4 meters wide. It has a very beautiful orange color. This is very nice. This is very beautiful. This is very beautiful. The orange color, the orange color, they have. have in contrast with the black winds. How big are these nests?

They are quite massive. So I will say so 1.5 meters wide and it has been accumulated through time. Some of them they were in deep like four meters. 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 over 10 feet deep.

Yes, they are quite deep. And they have been using through centuries by the birded vulture. Wow. Okay. So the nests were in use for hundreds of years by vultures. Yes, that's right. We consider that this nests has been accumulated for several centuries. This is what we didn't know.

We knew that these were historical nests. that the birded vulture left empty or non-use for the last 100 years, because the species has disappeared in this part of Spain. But we didn't know for how many years that burglar's vulture have been nesting in the same places over and over and over. So no, it wasn't until we dated by Carbon 14. 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. What were some of the other finds? What were the best nest finds? Well, we accessed 12 nest. 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. 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. So we achieved a proteomic analysis that gave us the result that this leather mask was made on a show. sheep. 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. Yeah. All the material that has been recovered in the nest provide with various information. So like what kind of trees were in the environment? They were used by the birded 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 led 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 main on grass. Yeah, I have to ask about the shoes. Why are birds using these artifacts in their nest? Like, why is it helpful to have a shoe in your nest? This is a very good question.

So in order to thermoregulate the temperature in the nest when they put the egg, is to bring material to keep warm the nests. But in this case, The bird found these shoes probably abandoned in the nature and considered, this will be very good to thermal regulate the temperature because it's thick and stable, and I will take it to my nest. So we found these different shoes in different nests, in different layers, and we dated some of them, and one of the shoes were from the 13th century,

So this means they have almost 800 years ago. Yeah, wow, 800 years, yeah. Yeah, and we dated also the fragment of the grass basket. And this is more recent. This is from the 18th 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 great surprises.

We've been talking about their nest building, but we need to spend a moment on their diet. How do they survive on bones? Well, this is the most surprising thing of this verdant vulture. 70, 80% of the diet are composed of bones. This animal is the last one in the trophic chain. So he doesn't compete with other carnivores or other vultures for getting access to the caronia carrion. So the flesh of the animal carcasses. No, we have videos of his behavior and he's just waiting for the others to finish.

and when the others have finished or he doesn't really compete or fight for food he eats the he select the bones and we see that he has a preference for the distal part of the legs basically the metapodiums and the phalanches because these bones has the highest grease content

on the animal skeleton So he usually select herbivores skeletons. So like sheep, goat, dears, this is what the animals they eat herbivores. So what he does is very curious. So he's flying. Imagine he's flying on the nature and suddenly he saw a carcasses of an skeleton of an animal. So he selected the long bones usually. and what he does is going up up to 7 to 80 meters

and then drop the bone on the mountain on an area where there are stones in order that the impact of the bone on the stones break the bones. Like seagulls with muscle shells? Yes. So in this way, he has this long bone in small pieces, which is easier, easier for him to swallow.

Doesn't seem that easy, though, even in small pieces. Well, but this is his behavior and how he understand that in that way can eat more easily the bones. And his pH is so low that he has the capacity of a, digested the bones because neither of us will even hyenas could really digest the bones. But he does. The stomach acid just melts those bones. Totally melted. And when we see his feces, they are chalk.

Chalk. Wow. You know, you write that these birds, the bearded vulture nests are natural museums. Tell me about that idea. Well, it's because otherwise we wouldn't have recovered these human-made artifacts and is opening us a new line of research to investigate all the different vegetable materials, different grasses, to make these shoes, to make this basket. So we are planning now to investigate the different techniques used for this,

humans through time. And obviously we need to date it, everything, in order to know for how long this nest has been occupied. I can't wait to find out. Yeah, me, 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 going to be really, really cool. Well, good. luck. Study author, Dr. Anna Belan, Marine, Arroyo, an archaeologist and professor at the University of Cantabria in Spain. Anna, thank you so much for joining me today. Thank you very much for your interest, and it was a pleasure. Today's episode was produced by Rasha Aireti. I'm Flora Lichtman. Thanks for listening.