Edible bird’s nest, one of the most expensive animal products people eat, is made from the hardened saliva of swiftlets, not swallows. This episode explains how male swiftlets spend about 35 days building nests from strands of saliva, why the nests are prized for their gelatinous texture, and why their high protein content may be hard for the human body to digest.

We follow the trade from dangerous harvests in limestone caves to purpose-built concrete nesting houses, which now supply an industry estimated at $8.5 billion, with China accounting for over 90% of consumption. We also look at the rare red nest, counterfeit products, and the forensic science and bird flu rules that govern the trade.

• Why yan wo, often translated as swallow’s nest, actually comes from swiftlets related to hummingbirds
• What the glycoprotein makeup of the nest means for its nutrition and digestibility
• The dangers faced by nest gatherers who climb bamboo ladders in pitch-black caves
• How guano vapors, not blood, turn nests red, and why researchers link this to high nitrite levels
• How RFID tracking, PCR testing, and gel electrophoresis catch fakes and trace where nests came from