If your working on the clip with the wings:
If you 'shrink' the clip, the mask will move with it. Set the start point of the mask and start size of the clip.
Then set the end size of the clip, then adjust the mask at that point to the size you want.
Odds are good you'll have to adjust the mask at several points along the way, if not all of them.
If your looking 'through' the wing clip's mask at a track below it:
Just shrink/move the 'lower' clip around. The wing clip is like a window your'e looking through.