I don’t know either but speculate the hens move to areas that are warmer in the evenings so they can go out and feed themselves while the sun and air temperatures keep the eggs warm.I'm not sure what makes them do that or why they travel to the area that they do. The place I hunt north of me they are on my on my place from about the end of Feb through May, and I'll never see them again until the Feb. May thru January they spend all their time 2 miles to the southeast, and it looks nearly identical to the place I hunt lol.
I’ll give an example. Where we live in Osage County, it’s up on a ridge. A buddy lives on the other side of the same ridge 3 miles East.
He sees hens during the fall and winter. No Tom’s.
West of him we see Tom’s year around, probably because we keep a corn feeder running year around for the wife to watch deer.
In the spring the hens show up, breeding activity and gobbles for days on end.
Then we see hens out on the West side of that ridge in evenings out by themselves which in my mind means they are nesting. Same hens every day in the same location out in the pastures.
Those have been my observations, repeated yearly with the same scenario.