The more valuable white-nest swiftlet nests are initially collected in February, and again in June and July. The breeding patterns of the birds are not rigid and must be closely monitored to accommodate any observable changes in their reproductive behavior. The birds' nest harvesters who are called tukang pemungut still employ time tested techniques that have been used for hundreds of years. The pietau , is another ladder which usually consist of a rigid bamboo pole about 25 metres long. Rungs are fastened across the bamboo as steps, and additional rattan cords are tied around it to offer some security to the climber.
Harvesters use a sesungkit to remove the nests which are just out of reach.
It is a thin hand-held stick of bamboo or light hardwood which has four sharp steel or bamboo points to dislodge the nests from the cave surface. The harvester must assess the best combination of these props to be used, based on experience and the location of the nests. When collected, the nests are placed in the ambong , a woven basket which is then lowered to assistants who empty the nests into a large sack. Other activities Besides observing the exciting display of skill and courage by the birds' nest harvesters, another activity for keen naturalists would be to watch the cave empty of its 2 million or so resident bats as they spiral out for their evening feed. This usually occurs between 5.15 - 6.15pm, but rain sometimes delays or cancel their showing.