The Baby Robin's Eye View and Mine

Last year at summer's end, I discovered a robin's nest tucked safely into the beams of our second floor balcony. Because robins often return to the same nest each year, I left it undisturbed. Yesterday morning I discovered it had indeed been used again! At first glance I saw 3 wide open beaks waiting impatiently for food. My second visit discovered 3 mature babies all lined up on the cedars, and finally, when I photographed the nest, just one baby and a parent dutifully watching from afar (as detailed below). This morning, the nest was empty. So far, I've been unable to determine if they are temporarily absent from the nest for flying lessons, or if they flew the nest entirely.