Here is a link to a very interesting internal layer post here on BYC with pictures. I guess it could be graphic for some but maybe it will help. This is a chicken but I am sure it's close to the same thing.
https://www.backyardchickens.com/forum/viewtopic.php?id=186940
https://www.backyardchickens.com/forum/viewtopic.php?id=186940