Noise of chicks ‘turns off’ broody instinct
Q If I put some eggs under a known good broody, how does she know how long to sit? A Victoria says: There is pure instinct working here. A hen goes broody when her hormones tell her to. Usually if she thinks she has laid a clutch, she stops laying and sits on the eggs, turning them several times a day and taking about 15 minutes each day to defecate, eat and drink. She will sit on them until she hears cheeping — with chickens this is around day 19 as they hatch on day 21. With ducks, the broody hen or duck will hear the ducklings at around day 26 as they hatch on day 28. The hen talks back to the emergent chicks and their cheeps turn her brooding instinct into the maternal protective instinct. Thus it is the noise of the chicks that determines how long she will brood the eggs.
A chick’s cheep will turn a hen’s brooding instinct into the maternal protective instinct