[TZubiri]

Have you taken a look at Picture Insect and Picture this (for plants, original). the incumbents are very specialized, making a simple app for all nature sounds ambitious. I never did find one for bird sounds, but that would be an interesting niche.

[anotherpaul]

Isn't Merlin the birdsound app that is commonly used?

https://merlin.allaboutbirds.org/