A 700-year-old-plus sandal made of woven twigs and grasses is the oldest artifact to date found among the bearded vulture nests examined. Sergio Couto

The bearded vulture , a large bird of prey with an unusual diet consisting primarily of bones, has long fascinated ornithologists. But now, a new study has shown why the bone-eating birds could be even more intriguing than once thought. Their carefully crafted nests, serving multiple generations, may also act as “ natural museums ,” preserving centuries-old cultural artifacts, according to scientists.

In Spain, researchers studied a dozen bearded vulture nests between 2008 and 2014. The team analyzed them layer by layer, uncovering over 200 human-made objects that the birds may have repurposed as building materials. Carbon dating of

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