fledge
verb no object
(of a young bird) develop wing feathers that are large enough for flight:
ひな鳥が育つ
e.g. the young fledge around four weeks after hatching.
with object bring up (a young bird) until its wing feathers are developed enough for flight:
ひな鳥を育てる
e.g. they fledged twenty-four chicks in fourteen months.
ORIGIN
mid 16th century: from the obsolete adjective fledge ‘ready to fly’, from Old English, of Germanic origin; related to Dutch vlug ‘quick, agile’, also to fly1.