Oh, one more thought, once you get your post editing program, make sure you shoot in RAW and not jpg. Another great reason to use a post editor. 
The fully automatic part is handled by your camera. The lens just does what it is told to. So, yes, it can be fully automatic.
You can get it from either of these fine retailers. Adorama or B&H Photo <click either.
I got mine form B&H Photo. I bought the big Tamron here locally because I wanted to try it first. We have a nice camera store, Overland Photo Supply, and they let me play with it and try it before I bought it. There has been some negative reports associated with the Tammy. My copy is fine.
Keep in mind, for birding, you really need 500mm or more. The more the better, otherwise you have to get very close. And in fact that is the choice, get closer or go bigger! Most folks mistakenly think a telephoto lens is for taking pictures of stuff a long, long way away. Of course that do that but there real job it to fill the frame with the subject. And that usually involves getting closer. I was probably 25+/- feet from the titmouse. You will love the Siggy but be warned there is a learning curve for using a 500mm super telephoto.
