Last evening there were three nestlings. During the day and evening I watched totally stupid adults get too close to and touch the nest. They thought that was funny. Refused to back off when asked to back off. This morning there were only two nestlings. Yes, it's possible that the parent robins knew that one nestling was weak, but I feel very strongly that the demise of the missing baby is due to human interference. The images are from yesterday, a memorial to the trio, and then today, twins.