A few years ago while doing some field research, heard the oddest noise while walking by some species of hawthorn tree. It sounded like someone running a coin along the face of an old washboard. I looked around and it was a Blue Jay! It was an alarm call as I was too close to a nest in that tree. Got out my mirror and saw three nestlings.
From then on, checked on them from a distance using binoculars until the nestlings successfully fledged.
Heck of a good place build a nest - no chance of raccoons getting to the nestlings in that species of tree!
Not much chance of anything getting into a hawthorn tree. Those thorns are nasty and painful!
I love watching blackbirds attack hawks around here (SF Bay Area). The blackbirds are agile and nimble and can outfly the raptors. They peck at them in midair and eventually drive them off.