A high school diploma is often a one-way ticket out of the parental nest.

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In the animal kingdom, species that build nests often do so only to shelter the eggs that contain their offspring until they hatch. Frogs and sea turtles are done with their parental duties after laying eggs in a secluded nest, while wasps and alligators keep their young in the nest until they're mature enough to care for themselves. For alligators, though, that time period may only be about a year. It's clear that as humans, we invest far more time and effort into caring for children while they're under our roof.

Though humans spend more time with their young than nest-building birds, there comes a time when avian metaphors begin to apply very aptly to children. We often speak of young adults learning to spread their wings and fly; they go off to college or the military, get married or accept a job cross-country. Whatever the child's flight path, parents are left with an empty place in the home, or as it has been dubbed in the vernacular, the empty nest.

­Though the departure of each child brings about unique and significant changes, it isn't until that last child is no longer living at home that you have an official empty nest. The occasion of the last child leaving home could bring a sigh of relief to the dad that no longer has to worry about Junior borrowing the family car on Saturday night and returning it with an empty gas tank the next day. Mom no longer has to clean up and stock the fridge after her daughter's friends ar­e over. Sure, the house may be quiet, but that means more time for new hobbies, date nights and travels. It can be quite exhilarating for a parent to watch a child entering a new phase of life, particularly when the parent is proud of the job done preparing the child for this moment.

Other parents, however, have a harder time dealing with the departure of a child. When the loss has a negative impact on a parent's daily life, it's sometimes referred to as empty nest syndrome. On the next page, we'll take a closer look at this condition.