I have an 8-month old speckled Sussex that has started behavior that resembles "broody practice". She's going in a nest box to sit even if it's not her time to lay and she growled at me when I opened the door the other day (that's completely new...) She's not staying put yet but I have high hopes for spring. I understand that Sussex are supposed to be prone to broodiness and they're certainly big enough to cover more than a few eggs.