I had a hen go broody a few days ago and going to try hatching for first time. She's on golf balls now, and I have seen it is suggested to swap them at night. This is better than swapping when she gets up to eat? Since I am going out of town the first part of June, I am not giving her eggs until next Wednesday so I can be back on the expected hatch day. I am going to move the other 6 chickens to another pen tomorrow so I dont have to worry about any shenanigans from them or food being not available for her while I am gone.
That all sounds good and advisable. You can swap them at night or during the daytime. A devoted broody won't care. She'll just glare at you and roll the eggs under her, clucking. If you are afraid of her pecking, you can add from the tail end pretty successfully. If she is at all nervous, night time is then better...but I've never had any issues giving eggs once a hen was truly broody. Taking eggs from her is another matter!
Good luck and keep us posted.
Lady of McCamley