I'm going to assume the attacks were from mockingbirds. They're vicious winged fiends when it comes to dogs and cats within 3 miles of their nesting spot, and I don't get how most people don't realize how aggressive they are. They've divebombed both my dogs and my friend's cats on numerous occasions.
I totally agree, birds do attack for the fun of it. Once, I was almost thrown down the roof of a building by a seagull. I was sitting on the edge, and I noticed it circling me. I thought I was being paranoiac, but when it disappeared from view, I turned abruptly and I saw it zooming towards me. Hell, I even felt the the air rushing on the top of my head. Crazy animal!