Failed nests

This is the time of the breeding season when I sadly discover nests that had a happy family a week or two ago, are now empty. Sometimes I find no trace of any ospreys, sometimes I find an adult perched in a tree near the nest. I search for bodies when I can. I have found several nests like this in the past few days. It's frustrating to have no certain explanation for the failures. The most likely causes are that a chick got blown out of the nest in a storm or the nest was predated. The likely suspect is a Great Horned Owl. If I get to the nest soon enough I may find bodies, often with the head missing...the calling card of an owl. But other ground predators may have carried away the bodies by the time I discover the nest empty. I search for the adults in the surrounding area. We are also approaching one of the dangerous passages for chicks...fledging. Not all first flights go well. If they fly away and are never seen again, it must be assumed that the chick got into some kind of trouble. Most chicks first flights are a short loop and back to the nest, or to a safe, but often awkward landing on some nearby perch. From what I have observed, flying is easy, landing is hard! I search for chicks missing from the nest...and usually can find them. When the male brings a fish, most chicks come screaming. To call a nest successful, it must be determined that at least one chick fledged successfully.