References in the literature to nest-visiting are usually very specific, to purpose and breed. For example, cowbirds and cuckoos lay their eggs in other birds' nests, letting the owners breed their young, and a variety of birds, like jays and crows, have been known to steal eggs out of other birds' nests, for food. I've watched a crow fly off with a baby bird, after furtively visiting the nest in question. Some birds will out and out take over the nests of others.
But never have I found any anecdotal material on cardinals visiting the nests of other birds, so something I observed one night caught my interest.
At one of the hospitals where I worked, we had been watching with delight a robin couple raising their babies in the dogwood tree in front of the lobby window. One night, we spotted all too late the stalking of a stray cat, who had gone up the branches and knocked the babies out of the nest. The parents were nowhere in sight.
We ran out and put the birds back into the nest. We just couldn't leave them there on the ground, if they had any chance at all of surviving the shock. (And by the way, it's not true what they say about human scent driving off the parents. Though humans themselves will drive off the parents.) They were still living, at that moment, though it was touch and go for them, and they passed within an hour or so. But before their last breaths, about 3am, a cardinal couple kept coming over. They were looking in on the baby robins, and I half-fancied that they were considering taking over the care of them. They were tilting and lowering their heads as if to hear better --- they were listening to the babies... (No, the babies were far too large for them to be preying upon them --)
We none of us can know for sure what they were considering, but a thought came over me that they knew they had come to witness the death of those babies.
I leave the matter to your imagination ...
Cardinal in Snow