I have been giving my 2.5 week old Mallard and Rouen and 1.5 week old Mallard ducklings some greens (romaine) which I have been chopping up very finely. They go nuts! How much should I be giving them? They go through what I give them in less than 2 mins. I am not sure how much the little guys are even getting because the older Rouen and Mallard are voracious when it comes to greens. And how often should I give it to them? I tried to search the info but couldn't find anything specific. There are 4 of the critters in total. Thanks!