|Here are several other articles about weird eggs. If your bird has laid one, it might be an isolated case or a sign of big trouble. For your bird's sake take the time to read these and understand.|
Internal and False Layer
Sometimes when a bird lays an egg it does not come down the oviduct as planned. Usually due to a Hormone Imbalance it will reverse course and fall back into the body cavity and at some point in time may or may not be reabsorbed by the bird's body.
This egg appears to be one that was not absorbed in the body cavity but managed to make its way back into the oviduct and finally make its way out of the bird's body.
When the body tries to absorb an egg it will try to wall it off and surrounds it with a Calcium like material. This is one of the reasons why it may appear that several shells have been laid down.
It is also possible for an egg to be fertile and have the same reverse course episode. When these eggs are opened it may appear that there is tissue in the egg. They usually have somewhat of a foul odor but are not totally rotten.
Birds that are internal layers may have several ova back up into the body cavity. The body tries to absorb them and lays down the calcium. Upon opening the egg it will appear to have several eggs within an egg.
This kind of stuff is what keeps me interested and keeps me going. Birds are great.