When we were kids, my brother would choose the smalest chick or duck and feed it with flies. He would kill a fly with this special thing for killing flies (I have no idea if it has a name in Romanian, so, of course, I don't know the name in English :) ). Then call the duck or the chick. After a while, all of them knew that this sound *PLIOSK* meant that my brother has a snack for them :D. Of course, after eating so many flies, they were growing the biggest :)