how many days will a duck sit her nest after ducklings start to hatch?

[Quackers01]

Hi there I'm glad to c your ducklings. I have some great news as we'll I had a clutch of seventeen over the weekend I feel like a proud daddy even though I did not do much except wait impatiently I will try putting in a pic or two

 

[Quackers01]

Hi guys I cant seem to get the hang of this site yet. probably cause im on it so little. Non the less my ducklings are here 18. 6 black 12 yellow with a little black. question . is it normal for the mommy to attack so viciously the hand that feeds her and the babies, when helping a distressed duckling in the pond ??? Also big one, now that I have these ducklings I'm planing on keeping the females for eggs and the guys are hopefully gonna be joining us for Xmas lunch next year, is inbreeding permissible amongst ducks or do I have to swop my females out and get new ones in seen as how there daddy would be decking them ????