I think this ongoing blog review of the new 7d II by Artie Morris will be very helpful for bird photographers to make up their minds to buy it or not. Artie is known as one of the top bird photographers in North America and I personally learned a lot from following his blog on the 7d II. Needless to say that I have already ordered mine. He review only a few photos per day in detail. He regularly used the 7d II with his 600F4 IS II with a 2X III TC for an effective focal range of 1920mm. The results are astonishing taken into account the challenge of lens shake at that focal distance. You have to scroll back at least two weeks to start at the beginning of the review. I hope this is helpful.
http://www.birdsasart-blog.com/
http://www.birdsasart-blog.com/