I think this is the vital issue here, and why I agree with OP. There will always be boundaries to immersion in a game like this, and at the moment some people are exploiting those boundaries for an unfair advantage in the game. The notion of hearing the sound of birds flying away when someone suddenly spawns into the game is a rather elegant solution, i think. Particularly if the sound is intentionally made to be at least partly omnidirectional, it will alert the affected player(s) of a new and unavoidable variable in their gameplay. Making it audible also allows for less attentive players to miss it, meaning that it would not be noticed as much as an on-screen alert. To balance this effect, there should be a similar alert for the players spawning in. Something similarly audible, yet unobtrusive and within the environment of the game. This would not affect people attempting to abuse the mechanics of the game for an advantage, but would level out the heads-up given to the player already in-game.
