I've learned that the average incubation period for Pigeons is in the order of 17/18 days. I have no idea how old the egss were when I first discoveed them but that was 10 days ago. I have to assume that they will hatch any day now and certainly within the week.
Whichever of the two Pigeons is sitting on the eggs (because I believe the two partners share the role), the other is never far away and being extremely vigilant.
A few yards from the Laburnum tree that holds the nest is a huge Pine tree that commands a masterful view of the surrounding area. The non-sitting partner can usually be seen there, standing guard .... day and night.