Attack Bird

Ok, I promised you more about the bird attack, and here it is. This bird (who I know looks like a very nice bird sitting in his/her tree) would wait for people to pass the tree and then swoop down and attack them. He never made a frontal assault, just flew in from behind, swiped at the top of the head, then back to his/her tree. I didn't realize this when I passed the tree, and the first swoop I thought was a fluke, but then s/he hit my head a couple more times. Just past this tree was a little play area for the kids, so while they played I was able to observe this bird and I noted the following:
1. As stated before, it never attacked from the front.
2. It never announced it's intentions, or that you were somehow in its' territory, it just suddenly swooped.
3. It would only attack people in groups of 3 or less (and it seemed only if one or two of those were children.) Groups of 4 or more were safe AND children were safe.
4. It also seemed to avoid attacking people with hats on. (See, they are not only good for protecting you from the cold and sun.)