I knew somebody who had a pair of these and for birding I'd steer clear. They have a very narrow field of view and you will be constantly frustrated trying to pick things up in flight and dense vegetation. Also 8x20 suggests mediocre performance in low light. Don't be tempted by the Zeiss badge: I'm sure these are very good for general purpose use but definitely not for birding.
I have used the Olympus pci 8x24 and I know it's not like a full size bin. There are compromises with the compact size. The Olympus are great on value and price. I hope that Zeiss will be equal (if no better) than the Olympus because Zeiss are water resistant and more compact. I think they at little wider too.
But it's true that it's important a decent wide view. The kowa 6x30 have decent quality and respectables 400m at 1000m. Very easy to find birds, but again no compact at all. As I said before, compactness has it compromises.
Regards