Hi All,
I've been lurking for a while now so thought it'd be good to share my first proper attempts at bird photography and the experiences I've had with my lens combinations. For a bit of background, I've got a 550D which I've had for a fair few years now, and started with the 55 - 250mm kit lens. I then went for the Sigma 150 - 500mm which I tried for quite some time before getting fed up with it's softness. After borrowing a mate's Canon 100mm f2.8L Macro, I couldn't go back to non-L lenses, so after much deliberation decided on a 70 - 200mm f2.8 IS II with Canon 2x Extender III. I haven't looked back since (anyone in Aus want to buy a Sigma 150 - 500?!)! All of the shots I've posted here were with the 550D + 70 - 200 f2.8 IS II + 2x Extender III (except the currawong, which was without the extender).
I've never shot with any other L-series lenses (aside from the 100mm macro), so don't really have anything to compare to, but I'm so stoked with how sharp the 70 - 200 with the 2x extender is - in my experience it can be just as sharp with the extender as without (as far as the limitations of the 550D will allow). My only gripe is that the autofocus is a little slow (but still on par with the Sigma and faster than everything else i've got), but I'm hoping that will improve when I upgrade to the 7D II when it arrives

Can anyone give me their thoughts on whether or not that is correct - will autofocus speed and accuracy improve significantly if and when I upgrade from a 550D to a 7D II (or just a 7D if I can't afford the new one)?
Anyway, hope you enjoy the pics, I'm happy to post some more (plenty more where these came from) if people are still curious about the performance of the 70 - 200 with 2x extender.