Destoryed Killdeer Eggs

We went to see Mrs. Deer. We saw her flying and yelling in distress. She landed in a field and yelled some more. After about 5 minutes. She flew away, also yelling. We saw 2 destroyed eggs. There were 4 eggs so I’m not sure what happened to the other two. What do you think would do this?

Cornell Lab of Ornithology

Cornell Lab of Ornithology