Nestling pigeon.

Hi, We have a Wood pigeon nest in the clematis on the front of our house. The pigeon has sat on the eggs and now the baby or babies are fluffy. We havent seen mum in about 24hrs. I have trained my trail camera on the nest this morning for a couple of hours but no sign of any parent coming to feed. I've put it on again at 1pm till 3pm. What do I do if no sign of parent coming to feed? I hate to think of them there with no food. Liz.