Any tells you that the A7r4 is not a birding camera then tell them they have got it wrong, I am a wildlife photographer of 10 years using Canon, Nikon, Panasonic APS-C Micro Four Thirds, and now Full Frame.
The Sony A7r4 is the best camera i have had the pleasure to use it makes photography fun again and so enjoyable. The keeper rate is just bind blowing and when you come home i am spoilt for choice which image to pick from.
Even when i put the 1.4 extender on i was hitting 8 out of ten in focus. The bird is not an Eagle or Osprey against a blue sky, it is a small bird flying at high speed across water with glare. So take a look at this Turnstone with the extender on.
I turned up took about 100 images and came back in 40 mins over the moon with the results of this fantastic combination.