Over the course of the past 400 years, bird's nests have been prized as a delicacy in China; currently, Hong Kong and the United States account for the majority of the nests imported worldwide.
The swiftlet bird's saliva is used to construct these nests, which are then collected from cliffs and caves where they are found. It is widely held that the nests have numerous health benefits, including the ability to strengthen the immune system and improve digestion.