The Kepala Batas BH is my third test case where I run two different sounds at one time.
The first BH tested with running two external sounds was at Lenggong, Perak.
My second test case was at Segamat, Johor.
And my latest is at Kepala Batas, Penang.
These three BHs are doing well but is still under my close observations.
The key to the two external sounds will be the proper selection of both sounds.
What I did was to test all the good sounds in my collection at the specific BH and choose the two that attract the most number of birds to the rooftop.
Once the two were selected I will try to run one on the last tango tweeters and one as my main external sound.
The last tango sound is played only at prime time (three or four times a day) while the main external will run from 6:30 am until 9:00 pm, non stop.
The sound combination seems to double the number of birds to the BH.
Some were attracted to the main sound but some will be attracted to the Last Tango sound played.
You will be surprise to see that many of them will be attracted to both.
When both are running simultaneously they become frenzy and start to search for a window to enter.
Many will start to enter the main entrance hole and will start flying around all over the place inside your monkey house enclosure.
If you are able to pull them into your nesting rooms you stand a very good chance to turn them into your tenants.
The way to go is to plan very carefully how to install those external sound tweeters inside the monkey house enclosure and lure them towards your VIP rooms.
If you are smart I think you will catch them a couple at a time.
If one day you can lure one couple, within one year you will have 365 couples.
Let them stay and adopt your BH and when you have them inside you can start to "Kickstart" their nest building.
Use my idea of NKS procedures and I am sure you will be able to trap them inside.