Hello,
This is normal. Many animals if they sense something is wrong, will cannibalize the offspring because the know something is a miss. We see this in Dogs, and rodents as well as other species of animals. You may want to candle the eggs and remove the infertile ones. This may save on a lot of problems later on. I used to raise Rhode Island Reds and White Leghorns. We enjoyed them as pets as well as very good layers. I miss having them now. I raised most from chicks. I hope all is well with the ducks. Joan
I will give you a link with step by step directions. Joan
http://shilala.homestead.com/candling.html This will show pictures.
Veterinary Technician
I am Vet Tech. for 30+yrs. who works with all animals. I do alot of rescue work with small animals.