After the nestlings are born it is the female who is responsible for the care and rearing of the young. Have you ever wondered how long this whole process takes? Well, by human standards it only takes a slit second versus the 18 -21 years of age for your child to reach adulthood. The nestlings will leave the nest after only 21 days. I don’t know about you, but to me that doesn’t seem like enough time to prepare the young how to face all the challenges of survival. This must be nature’s way to trying to ensure that the various species of hummingbirds will continue well into the future.