Birdman of Alcatraz (1962)

As an inmate at Leavenworth prison, Robert Stroud has a series of confrontations with the guards and with the other convicts. When Stroud kills a guard, he is sentenced to be executed, and only his mother's impassioned intervention gets his sentence commuted to life imprisonment, which he must serve in solitary confinement. As he serves out his sentence in boredom and despair, one day he finds a helpless baby sparrow in the exercise yard. Stroud soon takes a deep interest in caring for birds, which gives him a new purpose in life, but which also brings new conflicts with prison authorities.