fledge
To grow flight feathers and leave the nest for first time.
To fledge means to grow the feathers needed for flight and leave the nest for the first time. When baby birds fledge, they've developed enough to take that first leap into the air. A fledgling is a young bird that has just fledged or is about to: it has most of its feathers but is still learning to fly well and find food on its own.
The word captures a crucial moment of independence. Parent birds don't push their babies out randomly. They wait until the young bird's feathers are strong enough and its wings are ready. Even after fledging, young birds often stay near their parents for a while, learning the skills they'll need to survive.
People sometimes use fledgling to describe anything new and inexperienced: a fledgling company just starting out, a fledgling friendship beginning to form, or a fledgling democracy taking its first uncertain steps. The word suggests potential and promise, but also vulnerability. Just as a fledgling robin might hop awkwardly on the ground before mastering flight, new ventures often stumble before they soar.
When ornithologists (scientists who study birds) say a species has fledged successfully, they mean the young birds made it out of the nest and began life outside it, which is an important measure of whether a bird population is healthy.