I included the function that identifies the obstacles on the route of flight (who kindly informed me Cameni) in the command script of the flock of birds.
Now, from my tests, even flying in the narrow gorges between the mountains, you will not lose any more bird.
This, however, is not assured "absolutely"!
For a purely "aesthetic" factor I have commanded the change of course "the last moment" because I really like to see the eagles that graze the cliffs ...
Since the flight of birds is very "random", it could happen that one set of unfavorable combinations fail to prevent a collision with the ground ...
In my tests it never happened but I only tried it for about half an hour .... and it is not enough to offer guarantees!
Here is the link to download the new script replaces the old EAGLE_Flock.js
https://drive.google.com/file/d/0B6114pZ3kPTgR2MyajU2MExIZXM/view?usp=sharingStill .... good flight!