I have two bird boxes on my garage wall they are three foot apart and both fitted with cameras. This year bluetits nested in one and fledged six young. In the other Robin,s nested and they fledged five young. While the female Robin was sitting she was being fed costantly by the male and very rarely left the nest. After the young had fledged she relined the nest and laid another five eggs which I am glad to say have all hatched and are now four days old but this time there is no sign of the male robin at all, she left the nest to feed herself  on regular occasions and now with five young she is the only one feeding them. Does this happen often or is this a very rare thing ?