Just as everyone else says, the 7 is lighter, has better iOS, and it has an aps-c so you get better zoom. The advantages of the 1d3 are the 10fps and the focusing if you get a good copy.
I test 3 copies, all perfect, but the focus was still weird.
My advice is to wait for the 7d mark ii if there is one, because even though the 7d is great, pros who want a small sensor for wildlife want a better camera.
But in your case, a 7d is the way to go, the 7d2 will be way more expensive, the 1d3 is to risky, and the 1d4 won't have a major price drop till a 7dii comes out.