This will happened in any BH that was wrongly designed.
The nests distribution goes haywire.
A good and well designed BH plus proper entrance hole orientation will usually gives a kind of nests distribution as follows:
If you have say 300 nests, the lowest floor will have 200 nests, the second floor may be 60 nest and the top most floor is 40 nests.
Yes most of those nests are at the lowest floor while the middle floor will have lesser but more than the top floor.
But this is not very common.
You want to know why?
Because most BHs are wrongly designed, wrongly orientated and the main entrance hole are not properly located.
I received a short message from a BH owner whose BH is in Sedili.
I was asked to revamp and at that time after 1 year 4 months into operation the number of nests was 2 (two).
Managed to check at this URL: http://swiftletfarming.blogspot.com/2013/10/sedili-bh-after-operating-for-1-year.html
Now he claimed that the total number of nests have increased to 40 plus 24 semi finished nests.
His complain now is that the nests were not properly distributed.
Most of the 40 complete nests were on the top floor (29) and bottom most (10).
Its middle floor only one (1).
So now what do you think we have to do?
The first thing that came to my mind was about his BH entrance hole(s).
I remember I opened two entrance holes.
One for the top most floor while the second using the wrongly designed monkey house for the 2nd and ground floor.
The first entrance hole was on the wall of the top most floor facing those flying home birds path.
While the second was a bit further.
No matter where those birds are staying I think he should not be overly worried.
He should blame the BH design.
If not because of my idea to open both entrance holes and at the same time hacked a big LAL on the 2nd floor he might have zero nest on the lowest floor.
I think the current result is outstanding as compared to his first 1 year and 4 months (only two nests).
Now after my revamped, about 1 year and 7 months, his nest number jumped by (40-2)/2 x 100 =1900%.
This is equivalent to 2 nests per month.
On the top of it he has another 24 semi finished nests coming soon.
A very good or I should say outstanding performances.
What I need to do now is to visit the BH perhaps change the external sound.
At the same time check on his BH humidity condition.
All those 24 semi finished nests must be NKS.
I hope I can teach him what to do.