Summary: When a baby robin leaves the nest you often find it struggling on the ground. Your instinct is to save the baby robin it by putting it back in its nest. There are two diverse opinions about taking such actions.
With an estimated population of over 320 million adult birds, the robin population is on the rise. Although estimates vary depending upon who is doing the estimating, robins that survive their first year are capable of living in the wild about five or six years. The oldest wild robin ever recorded lived for nearly fourteen years, but old age is rare in wild bird populations.
Robin females lay from three or four eggs the first nesting and another two eggs during the second nesting of the year, one egg per day. A robin will lay eggs even if she has not mated. These are unfertilized eggs that will never hatch and are eventually abandoned in the nest. Only about twenty-five percent of the newly hatched birds survive to become adults.
A mother robin does not begin the incubation period until all the eggs have been laid. This is done so all the babies hatch at the same time. Her body temperature is 104 degrees and she sheds her belly feathers to expose a brood patch. This featherless patch allows the female to press her bare skin onto the eggs. The brood patch has sensors that tell the bird how much time to spend on the eggs.
It takes about two weeks for the eggs to hatch and another two weeks for the babies to jump from their nest. This is where humans get a bit crazy. They see a baby bird on the ground and immediately think they need to rescue it. In fact, the adults, and especially the male robin, continue to watch over their fledglings for a short period. Some people want to take the bird to an animal shelter, but when this is done it upsets the balance of nature. Of all the baby robins that jump from their nest, only one in four is meant to survive. The others are meant to be food for the babies of other animals. That's why I'm always shouting "Don't mess with Mother Nature!"
If you pick the baby up and return it to the nest its instincts will have it jump from the nest again. Handling the bird will not necessarily cause the parent to abandon it, but, returning a bird to its nest may cause the parent to "kick" it out of the nest again. There is no such thing as nesting "overtime".
Another word about robin nests and predators. Moving a nest to a safer location, be it from other birds or your curious cat, probably will cause the parents to abandon that nest. The moved nest will appear to be a different nest to the parents. It's not only the nest that makes it recognizable. It's the surrounding landscape that is etched in their memories. That downspout or the gutter or a particular tree four is all part of the nest. Moving it to a new place would be like me moving your house to a different street. The house is familiar to you, but its location is all wrong.
Lastly, people think they can rescue abandoned baby birds. Again, those birds have been left for a reason. Perhaps the adult bird has sensed something wrong with the babies. Or, perhaps nearby predators have made the nest unsafe for the adult birds. Trying to raise a baby bird is nearly impossible without the proper tools. Regurgitated earthworms are just not an easy thing to replicate. Plus, baby birds need to be fed every few minutes from sunup to sundown, all day, everyday. Who is capable of handling such a task?
The balance of nature works. Some robins survive, while others don't. The population thrives if humans keep hands-off. Enjoy the birds from afar. They are not house pets and should not be treated as such.