I started leaving eggs when I wanted a hen to go broody... A little over a week later the worst thing ever happened. One broody... then two.. then three. And I have had at least one broody hen in one coop or another since then. Especially the ones I don't want broody have been broody!!!
We must have massive amounts of hormones floating around here. My australorp went broody in March, then 2 of the D"Anvers, now my Aussie is broody again setting on 10 eggs and yesterday my silver penciled cochin decides she wants babies. She is only 5 months old.