My two hens have been acting very strange for the past few weeks. It started with Martha acting broody and sitting on the nest all the time. Now it turns out that Gwen is constantly sitting on her head. They have two nests, but always shared since they were young. Gwen is always sitting on Martha's back, one facing forward and the other backwards. My grandmother thinks it might be because these two hens have never been around a rooster, and that gwen has taken on the role of trying to fertilize the eggs. They've been doing this for 2 weeks now, and not eating or drinking much. They are about 3 years old, and have always been together since birth. I got them when they were about 3 months old. What are they doing?