Most vultures are cliff nesters and carry food to their young in their crops. But bearded vultures (Gypaetus barbatus) usually deliver food in their beaks and talons. This means that well-protected bearded vulture nests in caves or those sheltered by rocky overhangs can accumulate animal remains and other material – including human-made artefacts used in nest building – over long periods of time.
Just how long has recently been revealed by a team of Spanish researchers, led by Antoni Margalida, who used careful archaeological methods to document the contents of abandoned nests, layer by layer. The findings were published in the journal Ecology.
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The bearded vulture, also known as the lammergeier, is Europe’s most threatened vulture species, with just over 300 breeding pairs surviving. Its diet mostly comprises bones, pieces of which may decompose quite slowly in suitable conditions.
Although the bearded vulture became locally extinct in southern Spain more than 70 years ago, the solidity of its nests and the stable temperature and low humidity in old breeding sites such as caves means that these structures and their contents can stay in good condition for hundreds of years.
To find out what has been preserved within them, researchers examined 12 abandoned nests in southern Spain, treating each as a small archaeological site. By carefully excavating layers, they uncovered 2,483 remains – mostly bones and eggshell fragments, along with more than 200 human-made objects. These included pieces of leather (one was ochre-painted sheep leather), cloth and objects woven from esparto – a common grass in the area, still used to make shoes and baskets today.
One striking find was a complete sandal made from esparto cord, carbon dated to around 650–700 years ago. Another was a crossbow bolt, though its age remains unknown.
The results also revealed that some nests had been used for centuries. One site was first constructed about 500 years before another nearby nest, showing that bearded vultures reused and rebuilt nests in the same areas over long timescales.
According to the researchers, studying these old nests offers valuable insight into how vultures interacted with their environment – and with humans. They say the work provides a new way to explore bird ecology, biodiversity trends and environmental change over time.
Top image: the sandal was found in a vulture nest in the Sierra Nevada mountains, Spain. Credit: Getty
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