All Zombeasts are destroyed by Flik Skyshiv and I believe also by Whirlpool.
Birdwatching does not give every zombeast its effect. I haven’t tried Warsong Wrangler.
I think zombeasts shouldn’t be all be considered copies, but if they are, “all copies” should be able to get buffs.
I suspect Birdwatching only considers “identical” Zombeasts as copies, not just the card name itself. If so, it should be fixed so it’s consistent.