For this tutorial I will tell u you how to make a crow fly around using path_corners.
1. Create a map, big enough for our crow to fly in. then in the map create an npc_crow, make it pretty high above the floor so it looks like its really flying.
2. Select the npc_crow and go to its object properties. Go to flags and check the "efficient" flag
3. Ok, now we made a crow, now we need to tell it where to fly. To do this, create four (or as many as you want) path_corner entities around the map. Make it the same height as the crow. Put the path_corners in a circle, so the crow flies in a circle. Name the first path_corner "path_corner1", make the second one "path_corner2", and so on.
4. Now, go to path_corner1 entity and open it properties. For next stop target put path_corner2. Go to path_corner2 and for next stop target put path_corner3, and so on. Make sure there is a yellow thin line connecting them.
5. Put the npc_crow wherever you want in the map. Open its properties and for first stop target put "path_corner1"
So, that’s it. When you spawn in the map the crow will fly to path_corner1, then that path_corner will tell the crow to fly to path_corner2, and so on. You can also configure the crows properties like its speed, for the way you want it.