Can layers all of a sudden think they're brooders?
Australorps are a breed that can be prone to going broody. And yes, it can happen overnight. Usually there is a gradual build up to a hen going all-out broody, starting with spending more and more time on the nest. Eventually she will sit day and night. When she's done that for 3 days in a row, you can be sure she's all-out broody. Then you can either put her in an elevated wire crate to 'break' her, or give her some fertile eggs to hatch, or wait 2 to 3 weeks and pop some day old chicks under her.
Edited by Ember13 - 5/9/16 at 5:51pm
Well you got few choices you can try to break her from it.. some people use cages or dog kennel. .
Or once she sets constantly you could get fertile eggs from online here or craigslist. .
Or you can buy chicks and put them under her at night.. you will have to let her set for awhile before doing that.
I hope you get an answer because I have a very similar scenario. My barred rock is still laying, eating and roosting but she is spending huge chunks of the day in the nest box, even without eggs. She appears healthy. When I remove her she goes right back. The other day after I knew her egg laying was done, I closed her off from the nest boxes and she got frantic. She raced all around the run bwaking. She actually tried "nesting" or hunkering under my largest hen who was standing. Several times. It was weird. She was sort of dive bombing herself under the other hen. Also, when I checked her breast I noticed she had plucked feathers out.
Sounds like your girl is flirting with the idea of going broody, but the hormone levels aren't high enough for her to go all the way broody.