she knows that if she places effort into her song, it will show that she has placed effort into her egg as well. surely, the hen who applies herself in all things will be found lacking in none
I had brown chickens in India, and she use to do exact same noise. I always use to hug and pick her up to release back on the floor in the room we kept chickens. We had 24 hens and 1 rooster. Funny days.
1. She's letting the other hens know where they should lay their own eggs so they're not scattered all over, and 2. she's calling the rooster (if there is one around) to escort her back to the flock