There is no sub-threat for world sound effect so I`ll just post it here.
And please I might be wrong about this threat as my earphones are pretty bad.

The other day I watched what I think was either a Dota-Cinema or Purge gamers game play and commentary and all of a sudden birds started squawking in the distance.It sounded like a murder of crows or something but it was only when Purge apologized for the noise that I realized it wasn`t in game, but the effect was quite something while watching the game play .I`ll try and find the video.

And I can understand that sound effects musn`t overwhelm or distract the player in a game but brief moments like this might make the world more believable. For instance I haven`t seen real wind effects in the trees and the sound of wind is absent but listening closely you can`t hear a lot of fauna.How about adding birds chirping ,crows squawking once in a while at the Dire side and the old black trees creaking ,frogs croaking at night near the river and crickets cricking,torch-bugs buzzing etc.

I think we as players easily miss the beauty of the game we play when we are to focused on strategy and winning and rightfully so,but adding small fluff like this when there isn`t any battles going on will only add to the mood of the artwork/lore and the realism of fantasy ,making Dota2 feel less robotic.