Years ago while I was living in Chico, CA, I got a demonstration of just how aggressive red shoulder black birds can be. I was riding down River road which has many thickets of black berry and cat tails. Putting alone at a stately 15 mph or so on a bright Summer morning, I was suddenly accosted by one really pissed off male red shoulder black bird who was diving bombing me and pecking at my helmet. At one point, he was low and slow enough that I actually swatted at him as he went past my face. Bad idea. He squawked loudly, and the next thing I knew, a black berry bramble about 20 yards in front to me erupted into a cloud of screaming black birds like something out of a Hitchcock movie. They descended on me, swooping and diving at me like a swarm of locusts. For a few seconds, all I could see was black feathers and beaks. It took everything I had to accelerate and get out of their "no bike zone" before being completely engulfed. Got home to discover both the bike and I were in dire need of a major clean up.