There is still three there. I've been watching most of the day. Plenty of flapping on the ledge, once or twice looked like a take off but back down off the ledge. The tercel (I think it was) brought a fair sized feed, ate most of it in front of the chicks. Just at the end fed one of the chicks before taking the carcass away. There must be logic there somewhere. It looked like they preparing for roosting so I left them to it.