Bird song app iPhone

Ive wondered about this myself.
If apps can identify music, even instrumental music, why not identify bird calls?
I have one of the Audubon bird apps that has a large library of bird calls in it.
Probably would require someone to build a database of bird calls the way music ID apps use some sort of database to look up songs the user is listening to.
Not sure if there would be enough of a demand, and maybe too many variations of bird calls to be able to work properly.
It would be nice, though.