I am not much of use with symbolism, but symbolism is what I was thinking with this text. The imagery is strong and clear to see the obvious. But, it sure is fun, and nerve wrecking, to wonder any symbolism there are in play and what in turn that then might mean. And all that without any idea if the choice of words is mere coincidence. I find myself hoping it wasn't to add appeal and entirely new context within the same text. Which is good and to the point to begin with.
Robins (at least from what I've read) are supposed to represent good parenting, and the essence of true adulthood earned independently. Taken in that context, what I see here, is an allegory: The death of the robin when it was coming of age, is a testament of the sad demise of purity in the youth, who're weaklings in hindsight. The ones who are supposed to be taking the mantle, are fading away, and there aren't that many of them left. Which is why, in the end, the necrotic elements of society are strengthening.