Yes you can. A hen that is working on laying a clutch of eggs to incubate will lay her last egg of the clutch and remain on the nest to go broody. You can set them immediately after being laid.
If your araucana pullet has been sitting for a few days you cannot put any other eggs with her. The chicks will be at different stages of development and some will hatch a few days earlier than the silkie eggs causing the hen to abandon the unhatched eggs as she takes what chicks she did hatch off the nest. If you want to set the silkie eggs under her you will have to take the araucana's eggs away first.
thanks. she is sitting but I change eggs every day. I don't have araucana roo and I don't want to hatch pullet's eggs. that's why I took silkie's eggs from my friends. I wanted ameraucanas for my olive egger project but unfortunately my friends have easter eggers and they didn't know it. people here sell ameraucanas with single combs
