Driving through the countryside in Kalimantan, Borneo, you can see huge three-story concrete structures with tiny windows—far larger than any house in the region. These are homes for the edible-nest swiftlet, a bird that makes its nest out of its own saliva hardened into a woven cup. The little white nests, about two inches across, are considered a delicacy in bird’s nest soup, one of the world’s most expensive foods, so they’re “harvested” in buildings designed to resemble the enormous rock caves where the birds normally nest.
