edit: Also, I watched the mother feed them a couple times. She just flew right between the two spikes without any issue, landing on the rim of the nest. This would definitely stop a larger predator though.
edit: Also their names are Binkbonk and Pikachu. I don't make the rules.
Grackles are so neat; always had a soft spot for them.
They've got smarts. I had to make sure they aren't in Corvidae while watching this. I couldn't get a better view of the nest and didn't want to scare the parents off, but it seemed like they really adapted the nest to the space and kept it surrounded by the spikes it's built into.