What settings for crown .25 for birds (Pest)

Hi
Cannot tell you the setting because my crown arrives next week. However as you know little birds little energy needed. From my 12 fpe .177 days for instance , a rabbit headshot only needs 1.6 ft lbs to kill, side or back preferably. I would wind it back as much as possible , get the right zero , mil dot scope helps. Biggest noise of course is pellet smack. If gun is harmonised as Ted says should be quieter too. 
There are some very silly regulations around the Nations of this planet. In France airguns with silencers fine but not PB 's . But you can easily buy a black powder gun, revolver or rifle. Must look a litlle denuded without the shroud. If you shoot static or prone maybe shoot from within a hide.

safe shooting