Some ideas to improve it even more:
Change the dirt block in the center of the Pokéball platform to glowstone/sea lantern and get rid of the torches. Would look cleaner that way.
Maybe add a few spawners inside the tree trunk, spawning some low level bird Pokémon (just some Pidgeys/Starlys between lvl 5 - 10 to populate it). That way it looks as if it's still populated.
Work on the terrain a bit. Add a little pond, one or two bushes and a bit of grass and flowers or so. that way the aviary theme gets more believable.
Change up the pillars a bit. Solid grey is a bit boring. Maybe change the middle row of Andesite to Diorite.