Sign Language question!?

Hi, guys! A few friends and I are learning sign language to The Rose for our school's talent show, and yes, we are doing it because of Napoleon Dynamite. Anywho, on Napoleon Dynamite, the signs don't match the words of the song because of some funky editing, and I was wondering what does the sign mean when they hook their thumbs together and flap their hands like birds's wings into the air. Does it really mean something? Thanks for reading!