When I first got my 24-70L, I went out on a sunny day and took some pics of birds, very much like yours, and noticed the same CA. I was worried too! I sent a pic to Canon, and they said that's well within normal range.
Well, the interesting thing is, now having the lens for the better part of a year, I don't notice CA anymore! It's odd, almost like the "problem" went away. Perhaps ADOBE CAMERA RAW now does a better job at default removing any CA. I don't honestly know! 

