When a bird opens its mouth, you’re most likely to hear a chirp. This is how birds communicate. They open their mouths and let out a series of chirps. Chirp chirp chirp!
The best place to experience the chirp chirping of birds is to offer them nachos(な). Birds love nachos so much, it's a guaranteed way to make the chirp with delight.
Currently there are no similar looking kanji which exist in the WaniKani learning system