Very cool concept!
Those cage-breakers really love to go to the farthest possible point from me to break the cage LOL. I like the dynamic when a power bird & a cage breaker show up at the same time, and you've gotta deal with the cage-breaker while also making sure that the power bird gets lured into the cage before it gets killed by your own towers.
I do wish the tooltip text was a little easier to read.