The mother seems to be wondering the same thing. The baby is too young to fly off and if it did it would still be nearby. Did something happen to it while both parents went fishing? It was not in the nest as I am always able to hear it and today it was silent. I find myself irrationally getting upset with the osprey parents for leaving it alone before it could defend itself. Last week I saw it by itself chirping loudly, crying out for its parents. On another day I saw it alone before the mother flew in, and she began screeching as three other birds flew overhead, becoming silent only when her life mate flew nearby and landed in a tree. The pair spent much time and effort for the arrival of the newborn, since I first saw them on November 25, now in vain.