That's a little disappointing that E-mount was crippled for action photography right from the get go so that video was better on them. My favorite thing to photograph is nature and wildlife, including birds.
Mine too. I shoot birds and wildlife probably 85% of the time. I do so with both a DSLR and an A6000 mirrorless. Birds in flight is a particular favorite specialty of mine.
Here's the thing: My A6000 is actually better and faster at tracking, more accurate, more reliable, and easier overall regardless of the size or speed of the bird, than my DSLR. Not that my DSLR is in any way bad - it's actually quite good, and has always been reliable for virtually any in flight tracking need I have. And it does have longer focal length lenses to work with, whereas the A6000 is limited to a 70-200mm F4 lens which is excellent, or a slower consumer 55-210mm with a 1.7x extender for a 357mm optical reach when I need more distance in a pinch.
The one thing I find may be missing from Mr. Friedman's comments is: when shooting birds in flight, even in the sunniest weather possible, it's extremely rare to almost non-existent to ever shoot at such small apertures, for the simple fact of needing fast shutter speeds...and for the fact that even when very very sunny, rather than stop down the aperture more, most BIF shooters will simply crank up the shutter speed even more. I can go through my BIF shots in sunny bright Florida over 5 different cameras and 6 years of DSLRs and mirrorless, and the number of BIF shots I have at smaller than F10 is about 30 shots...and they're all at F11. Vs over 7,000 shots, mostly ranging between F4 and F9. Despite a ridiculous abundance of sunlight here in Florida, I cannot dig up very many BIF shots at apertures smaller than F11. I went back 3 years through my DSLR shots, and found 6 shots at F11 and two at F13. None at anything smaller. And all of those were with relatively slow shutter speeds of 1/400 to 1/600, which means had I adjusted my shutter speed faster, it would have opened the aperture even more.
So in reality, I cannot see any situation where a mirrorless camera is going to be asked to shoot a bird in flight with an aperture set to F25 - even standing in the highest desert in the world at noon with no clouds in the sky. And that seems to match my real world experience, where the A6000's focus tracking is simply superb and practically faultless for BIF.
You can hate mirrorless cameras for as many reasons as you can come up with, but this 'focus tracking issue' simply doesn't apply for wildlife and bird in flight shooters - in fact, I'd love to find out if any BIF shooters with any DSLRs routinely find themselves shooting BIFs at F16 to F25...and if so, to know just what conditions they live in. I personally love my Alpha mount, love my DSLR, love my long lenses - and look forward to buying a future replacement which may well be the next SLT advancement. But I also love my A6000 mirrorless, and the very simple fact that it's one of the best BIF cameras I've ever used.
