A current inmate of a jail or prison cell is commonly called a jailbird, although the term can also be applied to those fortunate souls who have recently been released from those correctional facilities. A jailbird who snitches on his or her fellow inmates may also earn the title of canary or stool pigeon, since he or she chose to "sing" to the authorities.
The origin of the word jailbird can be traced back at least to medieval England, where convicts were often placed in iron cages suspended several feet above the ground. These cages were generally visible to passersby, who were routinely inspired to refer to the caged occupants as jailbirds, since they resembled real domesticated birds kept in real birdcages.
While the suspended prison cages may have given way to proper ground-level cells with improved hygienic and bedding conditions, the idea of viewing a convicted felon as a caged jailbird still continues to this day. Some released prisoners still refer to themselves as former jailbirds, which is often used as a more acceptable euphemism for "ex-con" or "inmate."
The average day of a jailed prisoner is not spent entirely behind bars, however. A prisoner may be assigned to a work detail within the prison walls, or spend part of his or her day in a supervised courtyard with other prisoners. Meals are generally consumed outside of a jail cell unless the inmate is being punished in solitary confinement or is in protective custody.
The "bird" in jailbird may also be connected with British slang for a prison sentence, as in the sense of "doing bird" for a crime. This particular usage may have fallen out of favor in modern times, but 18th and 19th century British citizens certainly knew what "doing bird" meant.
Early American slang also included a reference to African slaves as "blackbirds," which could just as easily be a reference to their captive status as much as their skin color.
Today, the term jailbird is considered more of a casual description of a person repeatedly incarcerated on minor charges such as public intoxication or petty theft.