If Eyes Watch From the Trees uses the threshold of *The Trees and Stones Speak of War*, do they get to Gather a Dahan afterwards? If so, when?

If Eyes Watch From the Trees uses the threshold of The Trees and Stones Speak of War, do they get to Gather a Dahan afterwards? If so, when?

Yes, they may Gather 1 Dahan into the target land after the Power is 100% finished (including the threshold, even if the threshold Pushes out all of the Dahan).
It works because The Trees and Stones Speak of War only adds Defend to a single land. (The threshold effect may then move some of that Defend around.)
Note that Eyes' bonus Gather will not move any Defend with the Dahan. That's a special feature of The Trees and Stones Speak of War.