Roy and I revisited Tom this evening to check upon the Tawny chicks. Mum was still (surprisingly) present and all three young were fine and healthy although the youngest was just too small to ring. The two elder siblings are 24 and 20 day's old and we think, by judging her moult pattern, that Mum is two year's old.
There is still plenty of food in the box and Dad is doing a wonderful job by providing for his family.
A fantastic evening and it is safe to say that Tom was very pleased and is looking forward to us going back to check upon the Barn Owls!