During my absence last week the eggs of the robin (Turdus migratorius) that has a nest above our mailbox hatched. This afternoon I photographed the nest amid the protests of the parents. Yes, I think there were 2 adult birds around. According to this source, both parents care for their offspring.
About 10 days ago there were 3 eggs in the nest. My wife says she saw 2 chicks last Tuesday. But there is only one chick visible in today's pictures. So it seems that natural selection has already removed 2 of the offspring of this pair.
The eyes of the surviving chick were still closed as of this afternoon.
Final update is here.