I cant say enough about the A7r4 from a birding point of view it is a joy to use and the keeper rate is unmatched to any body and Lens i have ever owned. If i miss a couple of images its because of user error, but its just fantastic the way it keeps track of the birds. Yes i know there not the fastest birds to judge a camera on, but you find me someone who posts images on a trusted review of Fast moving birds. There always Eagles or Osprey in fantastic light and perfect conditions.
I just love any bird and to look at the agility of the bird wing shapes and movement like a hawk the young gulls are very fast and never do the same thing twice so you act on impulse, but its lovely to see all the different positions they get into when you edit. I turned them to Black and White for a better look at the feather shape and detail.