In the version of the ambient sounds mod v3.1.7 on 1.12.2, birds sing at night, and this spoils the atmosphere. In the mod settings, you can only turn off the night singing of birds in the jungle, but not in other biomes, how can I make all the birds SHUT UP at night everywhere?

Answered you over on curseforge. Feel free to respond here if you have any further questions.

"You can however modify the engine via a resourcepack and overwrite the values for night volume" - where i can find this engine via a resourcepack?...

@Forturian yes you can. You can find all the files you can overwrite here: https://github.com/CreativeMD/AmbientSounds/tree/1.21/src/main/resources/assets/ambientsounds