Have a good look at the picture above and ask yourself.
Who do you think owned the new looking nest?
If I am right the neighbor must be the young swiftlet that was hatched and raised inside the old nest.
So if they like it so much to be very closed to their parent you need to do something about it.
Read my article at: http://swiftletfarming.blogspot.com/2013/09/will-those-young-birds-return-to-build.html
Enjoy reading my friend.
As usual I always have new things that I discovered.
Everything that was discovered is shared with you.