Particle arrival direction and orientation alignment.

[chriss3d]

Hello

I have been trying to achieve the effect which simulates birds arriving at the branches of a tree.
The tree branch is physX so there is interaction between trees and the birds. 
The problem is that  I'm stuck now  how to make the particles arrive only from the top of each branch side  in order to land properly.

How to make them arrive to landing only from one angle. I remember, from Pflow times,  that there was an option in find target op.  to make particles arrive only from object normal  side.

Any help would be great

Thanks

Best
Chris