There's a ring on my table

What in the world would convince a bird to go attack a biker's helmet while he was riding, then sit in the middle of the road and not fly away from tires of the big honkin SUV bearing down right behind the biker?

On the downside a little bird died, and probably in quite a lot of agony.

On the upside there was a big poof of feathers when it got hit, and that was by far the most comical thing I've seen all year.