Swiftlet sound use at diferrent stage

I did the random survey and conclude that less then 10% of the BH know the secret ingredient to be mix into the sound to make the sound more attractive.  This is one of the reason why less then 20% of BH did well among all.  You may wonder why your neighbor BH attract more swiftlet then your unit.

For me, I categories BH into 3 stages:
Stage 1 - Beginner (0 to 300 nest)
Stage 2 - Develop (301 to 800 nest)
Stage 3 - Stable (> 800 nest)

I use different set of sound in different stage.

The most difficult always at stage 1. Once you reach stage 2, you just need to maintain the BH in good condition & change you sound every 3 month to stay attractive. Stage 3 will be the starting point of the reward from you tenant.  You can started to harvest 1kg ++ per month & the nest continue to growth day by day. But the question is how to attract swiftlet to stay at you BH at the beginning stage. The answer is - CORRECT BIRDS CHIRP SOUND and STRATEGY to attract the birds. To be continue...