Most silkies are GREAT sitter, but then again all hens are different. I have a hen that will sit and sit and hatch out anything, shes also a great great mama hen. I have another silkie hen who will sit for 3 days then forget shes broody and go outside for the day and then remember and sit for another 2. It all depends on your birds, if this will be the first time your hens are broody and sitting I would put them in the bator just to be on the safe side. First time broodys arent always that great !! Maybe try giving the broody a few eggs that arent worth so much and see how that goes for next time. JMO !!