(American Ornithological Society Publications Office) Birds often choose their mates based on song, making it a key factor in separating species. However, analyzing spectrograms can only tell us so much — the characteristics that birds hone in on when identifying potential mates may not be the same ones scientists notice in audio recordings. A new study from The Auk: Ornithological Advances uses field experiments to ‘ask the birds themselves’ and uncovers as many as 21 previously unrecognized species.