|Buff Orpingtons and their cousins, Black Australorps are the usual culprits|
This spring I have at least five with the same aspirations. These ladies are so intent that they never leave the house to forage. In fact, I think they eat very little at all and their egg production suffers.
When the first of this batch to go broody, a Buff Orpington, started, I took eight eggs and set her on them in an empty rabbit hutch. The point of separating her is to keep her focused on her job (not really a problem) and to keep other hens from bothering her or adding fresh eggs to her clutch. After the required 21 days of confinement, she had not hatched a single one. I gave her a few extra days for good measure, but nothing.
Out of curiosity, I cracked all the eggs open. Several may have been unfertilized, or had just not gotten started properly, but a few had chicks in various stages of development. Two where nearly mature. I don't know exactly what went wrong, but I can think of a few things to change if I try again. For one, the cage was too big. She had to leave the nest to reach food and water. The extra space also allowed her to move the nest around when she turned her eggs, sometimes leaving one or two behind. For another, we tried this in early spring and the cold snaps may have been too much for the eggs.
Now the question is what to do with the five freeloading hens that are taking up valuable real estate that my layers need...