Hi Mike a lovely image of a very tricky little bird to make images of ,you have done really well to catch this one especially in the open with nothing in front.
Mike I'm learning I've not used your lens or camera ,but do use canon. I'd have pushed the iso here far more that you have. My reasoning very simple this is a fast twitchy little bird,I'd be pushing my shutter on the back of that iso as far as I could. Mike I feel this has cost you here,all around the bird seems sharp to me but maybe the bird is a bit soft. Mike I suspect i'm seeing a bit of motion blur. Mate as I say I'm learning my hope is that really someone more experienced will confirm the above ,or put me right,whichever we will both learn:S3:
Mike if you are not already aware Daniel Cadaux(super mod here) used this exact camera,it's worth having a dig on arties blog as well,Daniel did a blog there all about exposure with a 7D some wonderful images aswell, or simply have a chat.with him.
have a fantastic new year Mike
stu