15 Amazing Facts About 15 Birds

10. Swiftlet nests are a delicacy.

Some swiftlets, appropriately named edible-nest swiftlets, build nests almost exclusively from their hardened saliva. The saliva nests are considered a delicacy in some countries—in China, they are most frequently used to make bird’s nest soup—and are one of the most expensive foods in the world, despite having little flavor and no real nutritional value.