Does going broody happen overnight, or are there leading signs...

[Jeffross1968]

We've been noticing our first year EE sitting in the laying box on eggs every day the last couple days. But it's only while the run gate is closed. Once I've opened the gate, she tends to come flying out of the coop. But it looks as if she'd be there in the laying box all day if I didn't open the run to let them free range. Is this kind of behavior a sign of coming broodiness?

 

[Chickmate]

I have a first year Barred Rock that went broody like all of the sudden. I'm fairly new to chickens and never had a broody before. Two days ago she was in the nest when I went out in the morning to check for eggs and was still there in the afternoon. The day before she was out free-ranging with the others all day like normal. The next day she was in the nest again all day so I took her out in the afternoon put her in the yard with the flock. She stayed out for about 15 minutes and then went back to the nest box. Today I put her out with the flock again and she stayed out about 45 minutes before returning to the nest box. I keep taking her eggs away because I don't want chicks in the dead of winter. If it was spring or summer I'd let her hatch them out. I feel bad for her because she obviously wants to hatch eggs, but I'm not interested in being a grandma just now.