Robins gone

For the past 4 months I have had a family of robins, blackbirds and dunnocks living in a hollow bush on my patio. I have been feeding them with all the goodies and I see them all day every day. However two days ago I noticed I hadn't seen the robins. Not seen them since. The dunnocks and blackbirds are there and there is plenty of fresh food out so where have the robins gone? Lee