well, i suppose it comes mostly in the form of Pop, its like a branch of it. I guess it comes technical, like how Alternative is a branch of Rock.
Not trying to come across as bad but I can't find anything definitive that suggest it's an actual official genre. Is this just what people are deciding to call it? I've only found a few playlists. Outside of that nothing sufficient? Idk.
Birdcore is a actual genre of music that includes very meaningful music, such as my song Wish You Wish Stay, or other Lofi songs sometimes.