I love this song. It's so like edward speaking. I think it means that the guy fell in love with the girl but he let her go, then when he found her again, she was a completely different person. The flightless bird was the old personality of the girl which is the like, weak and gentle and the american mouth is the modern girl that he has found. At the second verse I think the guy was jealous and the mice were the guys surroundng his mice which is the girl. Lol. So edward-like.[perfection].