Looks like a tough spot for even a human to get to. There could even be wild bird’s eggs in the nest!
I have so many ideas running thru my head, but in the end, I would probably just wait and see what happens. If one falls/jumps out and survives the fall, she may go to its aid and abandon the others, or she may stay with the others and the chick will be left alone.
Hopefully it’s in a place that you can monitor closely and often. Best of luck!
And thanks for sharing! I’m anxious to see the outcome, as everyone is!