I just picked up 4 baby mallard/roun ducklings! They were born a few days ago. This is my first time with ducks and I have a few questions: 1.) Do they always shake when they eat? 2.) What should I do if I have no light? I put a heating pad underneath them. 3.) When can they swim? 4.) How big will they be in a few weeks? 5.) why are they so messy!?