It's pretty hard to stop a brood if her hormones (and genes) are telling her that she wants motherhood. Obviously her hormones are present whether there is a cock or not, but also obviously she won't hatch chicks without the rooster being present....but she doesn't know that.
You can try to discourage it or simply wait it out. [ Or, give her some eggs to hatch or chicks to foster, we can tell you how to do that on this thread
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Things that can discourage broody behavior are:
Consistently and frequently removing the eggs from her nest...if that doesn't work
Gently lift her out from the nest, set her in the yard away from the coop, and give her very yummy treats, repeat several times a day . Usually after a week of this, the hen will come running to you when she sees you, and in a few more days she is out in the yard most of the time (this is my favorite method)...over time this has worked for me.
Or you can try...
Blocking her from the nest....if that doesn't work
Moving her to another area altogether that doesn't allow her to nest....(she'll may just try to nest on the ground)
*Keeping her in less light (ie keeping her in less than 12 hours light each day so that she stops laying)
*Putting her in a hanging wire cage (to cool her down)
*Giving her an ice bath or applying ice compresses to her breast (her hormones are body temp related)
I don't like the more extreme methods of the last three...and honestly...I personally never discourage a sincere brood as I use eager brooders to hatch chicks. I only coax those who aren't committed to brooding (what I call sulking rather than really brooding....on again, off again, moving from nest to nest).
Broody behavior is controlled by hormones (linked to body temp and hours of daylight) and the genes, and some birds are simply determined to brood. If you can, let her do it.
I'm sure others will have some comments.
Lady of McCamley