Broken eggs on floor of coop - what might be happening?

[bobbieschicks]

I built my 3 nest boxes to be 12" high and 13" deep. Here's a pic of the girls sitting in them.


Lately I've been finding some of their eggs on the floor of the coop - and most of the time they're cracked. I'm wondering if they are knocking them out somehow when they get in or out, or if someone is getting in there to try and eat them? If I get to the egg immediately after it's been laid I can usually retrieve a good egg - although one time I found a crushed egg after the Orpington left. If I wait and check later - I will most likely find it on the floor of the coop smashed. I know that it could be because they are new layers and their pullet eggs aren't as strong as they could be even though they have oyster shell offered and layer feed. I've also found the Silkie's egg on the ground many times after she's left the nest box.

What do you think might be going on? Are the boxes too small? Is there an egg eater in there? Would a roll out nest box help solve these issues?
Thanks in advance!
Bobbie

 

[chicks2012]

You may need to add about a 3" piece of wood on the bottom ledge opening to prevent the eggs from get scratched out. Some people have boxes as small as 9" opening.