What could be more charming than a nest full of tiny birds being fed by the doting parents? Of course in time, we hope to see them venture out under parents' watchful eyes and try their wings.
The reality is not so idyllic. Perhaps you have found broken shells on the ground or more disturbing, dead or alive nestlings. I only have casual observation as well, but apparently not all birds leave the nest and many do not survive very long. Some experts suggest that most songbirds only live about a year. If that is an average age perhaps some live a few years but many die young. Except for banded birds it is hard to have good information on bird life.
The recent hailstorm here seem to account for at least two young birds in the small area of my yard. I found a young robin, still spotted on the breast but not full-grown beneath a hail beaten tree. Later I saw a much smaller barely fledged bird dead under another tree. Looking up for possible causes, I saw a nest, perhaps its former home, hanging upside down.
A day or so later I saw a young robin, perhaps a nestmate of the one found under the tree, still doing well. I was alerted to its presence by the loud chirping of a parent foraging on the lawn. Every time my dog or I moved near a certain juniper, the chirps got louder. Young robins and other species that can fly appear to still be protected by parents and fed at least part of their diet. This little one sat quietly while I photographed.
Predators, including dogs and cats seem to take their toll as well. How tempting is a young bird that doesn’t realize that sitting on the ground makes them quiet vulnerable? Unless parents warn them or dive-bomb the pets or predators, the young ones can be gone in an instant.
It is a little harder in most cases to really know about predators when birds are still in the nest. I have seen the vigorous defense of a nest tree put up by flycatchers when larger birds got too close. I later found egg fragments and young under the tree. I can only imagine what kind of nest raiding provokes small birds to mob hawks, owls and larger predatory birds.
Understanding the life or death struggles of birds and animals can present a dilemma. Do you intervene or let nature take its course? On whose side do you intervene? Predators are often seen as the bad guy but after all they have to eat too and they don’t eat grass and seed. Sometimes I have successfully helped small birds or at least distracted a cat from ending their short lives. Apparently the old rule that nest should never be touched or birds will abandon them does not hold true. Of course it is a risk to mess with nature. All kinds of unintended consequences can occur from you getting dive bombed to a bird dying in your hand.
I would rather not find dead birds or such but I can only do so much and most of that is to provide a place of trees and other cover, water and sometimes feed. The drama goes on in their short lives.