On a sad note, this morning after breakfast, I noticed one of the robin chicks was lying dead on the flagstone. We went out for a bit, came back, and two more were in the same spot, already dead.
Not too much of a mystery, with this fellow in the robin's nest. My suspicion is that this is a brood parasite: a bird that lays its egg in another bird's nest, and the adopted chick outcompetes its siblings for food, outgrows them, and when big enough, pushes them out of the nest, killing them.
I was tempted to knock the nest off it's rest, and destroy the parasite, but they have to live, too. It's the only way that birds with parasitic brood behavior can reproduce. It made me think about what it would be like to have to start life by killing your siblings. Apparently birds don't have those kinds of hangups.