I NOW KNOW HOW THEY DO IT!!!!!
I have a small flock of Buckeyes. One of our hens went broody so we put some eggs under her. Every day I find a couple of new eggs under her (unmarked so I know it isn't one I'm trying to hatch)I just thought other hens were laying in the box with her.
Today after I let the hens out, for treats she followed another hen back into the coop.
When I went back into the coop to feed and water them I noticed the broody in a different nesting box. "What are you doing in there?" The broody was strangely silient but puffed out. I grabbed her with one hand on each side expecting a lot of drama and complaining from her ...nothing she stayed real quiet.
While I was placing her back into the nest box with the clutch I felt a lump???? " what the #$%@ is this?"
here I found an egg up along her keel bone held tight to her skin by her breast feathers! She had been stealing eggs from the other nest boxes and carrying them tightly against her skin with the breast feathers.
Unbelievable!! Just to test the theory, I let her see me put the egg in the other box then I spied on her through the window. Sure enough the siren call of the other egg was too much for her. She went over to the other box nestled down on the egg stood up no egg! She walked over to the clutch box, climbed up and settled down again on the clutch. She had moved the egg to her nest box. Determined little cuss.
-Sub-