Phew, I know this is an old thread but first to come up when I did a search. My smallest one started to do this tonight. I was worried because she isn't feathering out as much as the other 2 and has always been slightly smaller. Then I saw her doing this. I thought she was dying and the others were picking on her, but then she gets up, runs around a little and then does it again. I was thinking about separating her until I googled and came across this. Relief!! Poor chicks were probably wondering why I was scolding them.
I could have written this post! This happened to me tonight and I called in my husband and son because she scared me so bad! She's also my smallest - an 11 day-old GLW.