If you hit F3 to toggle "
puzzle view"
you can see the diagonal path the wraithwing will take more easily. That path makes it look like it needs to be diverted 1 square to the east to avoid the arrow trap. Because of vertical preference, you'll actually need a horizontal wall of two skippers to make it go east (instead of north). So try to look for spots by the shore that you can get skippers to make a wall blocking it.
The skippers should got in the following positions:
Click here to view the secret text
×(17,17) (17,18) and (16,18)
____________________________
Links to neat forum tools that I always have trouble finding:
Click here to view the secret text