The neighbouring island to the resort island of Ko Phi Phi Don is a smaller island where no-one lives called Ko Phi Phi Lee.
The island is one big rock, but it is not a solid rock, it is a huge cave. This cave is the home to many animals, one of them is a small bird, the cave swift, which is a relation of the swallow.
This bird makes a very special nest for its eggs. The nest contains many nutrients, and is used in cooking to make bird’s nest soup.
It has been very popular in Chinese cooking for more than 400 years and it is very expensive. A regular nest will cost about US$50, but a special red nest can cost about US$2,000.
The male swift builds the nest in about a month on the cave wall. It is very difficult and very dangerous to collect these nests. The collectors are normally the sons and grandsons of past collectors and they are very strong and agile.
These people are very careful not to take too many nests, but, because the nests are so expensive, there are many thieves who will sometimes take all the nests from a cave and now the cave swift is an endangered species in many places.