Ok, I have been checking the samples provided with the pathfinding package, and in the scene Fsm_basic the "--calculated path--" gameObject and all is working well, I can trigger both events fine.
-- path will not be found if the destination is outside the nav mesh
-- pathfinding is a 2d thing, conforming to the navmesh, so it could be limiting for birds behavior indeed. I have requested this to Unity and they replied that they are aware of this limitation and it might get adressed in future releases, but for now, agent will have to conform to the navmesh.
What you could do is create a dummy agent ( with no mesh), and have your bird followin the agent, then you can adjust the height based on some parameters such as the distance from the base and the destination ( to take off and land).
As far as the integration in Playmaker, make sure you look at this fsm_basic scene, I focused quite a lot on this calculated path thing, so the fsm is suppose to cover most aspect of it ( simply move the targets outside the navmesh to fail it.
If you'd like to share your project, for me to have a look at it and better assess what could go wrong, feel free to pm me.