Canon 400 f/5.6L or Nikon (!) 200-500 f/5.6 ED VR (1 Viewer)

It might be worth getting the 400 5.6 first and trying it with your 650D before buying another camera. I have the 7D2 and love it, but I find myself using the centre point a lot for focusing, including for birds in flight. The extra speed on the 7D2 is also nice, but I got some images of Hobbies I was really pleased with with my 550D using the centre point when my 7D2 battery ran out recently

An update on my situation;
I found a like new Canon 400 f/5.6L on ebay for a good price and it arrived this weekend. So far I am impressed. The AF is slightly faster than the Sigma 100-300 f/4 and it is certainly sharper. The extra 100mm is already proving to be helpful. I have also decided to stick with the T4i and upgrade later, probably to a 7D II. The T4i has performed well and I see little need to upgrade to a 7D MkI right now. I've only been out with the 400 f/5.6L shortly around my feeders and the results have already been good.

Thanks for sharing your decisions, always nice to know, so many don't bother. Delighted you are pleased too.

Nice photograph Rapala.
I also did the stage upgrade like you did. My first issues that were limiting me was my kit lens of 70-200mm Canon with the Canon 500D body, and that was the AF and distance shots. I upgraded to the 400mm 5.6L and like you, found an instant increase in quality. The AF was not always the best though but rarely stuggled with birds being too close. Small birds are no problem, I think the only issue I had was large birds being larger than the frame. In San Francisco, I had to keep taking steps back for my first Hummingbird, although that was quite happy to wait for me to get my shot before moving on.

My next limit was frame rate of the 500D, as when I would take a burst shot of a diving bird, I would get one before entering the water and one after it left (none in the water). The new lens kept me happy for 1-2 years. I moved to 7D MkII as there was a really good deal at the UK Bird Fair a couple of years ago. This sorted out most of my issues, and I have rearranged all the buttons on the camera, allowing for me to switch to BIF mode at a touch of a button. That comes in handy as jumping from ground birds to BIF does not give you too much time to worry about settings.

That has been my current set up for the past 18 months, and do not know when it is likely to change. I tried a 1.4x convertor but preferred having the ability to use the view AF. I think my next bit of equipment is a decent computer as I make do with a laptop, which is very slow running Lightroom.

Rapala - FWIW, I currently also have the Canon 400 f5.6. Great lens. I use a 7d (along with my old 450d and a 100D). I think it was a good choice to stay with the old body and save for the 7DMK II
as you will be able to use a 1.4 teleconverter and still have autofocus on that camera. If you have the daylight, that lens will be a monster and still have very good image quality.
I'm currently considering the Sigma 150-600 contemporary which is now under $900USD to give me a little more reach...

Thank you all for the replies.
While considering the 400 f/5.6L I was skeptical about using low shutter speeds while shooting handheld. This hasn't seemed to be a big problem, especially given the photos below which were taken at 1/160 f/5.6 on a dark overcast day. Granted, the birds were static for the most part, but the sharpness is still pretty good and the photos acceptable. However, my keeper rate was not what it might be with shutter speeds at ~1/800+.

With the addition of the 400 f/5.6 and the loss of the Sigma 100-300 f/4 I can no longer cram the mounted 400 f/5.6 into my Tamrac Zuma 7 backpack as I did with the Sigma. I am considering the Tamrac Expedition 5x for the 400 f/5.6, binoculars, short zoom lens, and other accessories. The 5x looks very well made and solid. Has anyone any experience with this bag or recommendations for backpacks for similar gear? Thanks