From MySabah blog:
Chinese loves bird nest. Actually the nest is made of saliva from swiftlets. I have plenty of saliva in thick and thin forms for sale, if you are fond of eating saliva. Chinese says the bird nest contains minerals, rare protein and nutrients that keep you young and make your skin shines. There are two kinds of bird nests, i.e., (1) black bird nest, which contains 30% to 70% of feather, and (2) white bird nest, which has less feather and more expensive.
Madai Cave (Gua Madai), which is known as “Swiftlet Mountain” by locals, is one of the important producers of high-quality black bird nest in Sabah. You can see the limestone outcrop, where Madai Cave located, next to the road of Kunak, a small town between Tawau and Lahad Datu. It is the second biggest cave in Sabah.
Idahan people are the traditional owner of Madai Cave. For profit sharing, the cave is divided logically into different sections, which have different owner and can be passed on to their next generation. To visit the cave, you need to get a visitor pass at the security gate before you enter the village in the foothill. A guide will accompany you for a guided tour inside the cave, which is only a 10-minute away from the village.
Continue reading (incl. pics) at: Madai Cave, Kunak