In line behind Mom?? It's not uncommon to see C. Mergansers line up like this, usually behind Mom, who seems to be in charge. At our cottage we once had 31 young (probably three broods) being watched by one female adult(babysitter). Every once in a while they would suddenly line up behind Mom and swim away along the shore in a nice straight line - no fuss, no fooling, just following obediently.