My muscovy started laying eggs last week. I usually remove them daily, as we eat them. this time we decided to leave them and see if they would hatch. well............ I now have 23 eggs in the nest since last week. She is laying 2-4 per day. She sits on them almost all the time. She will get off to eat. How can I tell if they are fertile? What is a normal litter for them? I don't want 20 hatchlings. Advice?