Ducklings have started hatching, why does the mom want the eggs still?

[GarnerZoo]

This is my first time with ducklings and the mom is keeping the hatched eggs under her, she gets mad when I try to take them. There are still some un hatched eggs that have started pipping and they're getting a little pushed out, is this normal?

 

[Amiga]

Sounds normal to me - momma ducks may not want any help at this very vulnerable point for themselves and the ducklings.