Prisoners locked in their cells for days on end report walls speckled with feces and blood. Birds have moved in, leaving droppings on the food trays and ice bags handed out to keep inmates cool. Blocked from visiting the law library, prisoners say they have missed court deadlines and jeopardized appeals. Unable to access toilet paper, one prisoner tore his clothing into patches to use for tissue.

One thousand inmates incarcerated at Waupun Correctional Institution, a maximum-security prison in southeast Wisconsin, have been confined mostly to their cells for more than four months, ever since prison officials locked down the facility and halted many programs and services.

More than two dozen inmates at Waupun, the state’s oldest prison, have revealed to The New York Times that since late March they have been forced to eat all meals in their cells, received no visits from friends or family, seen complaints of pain ignored and been allowed limited, if any, fresh air or recreation time.

The state’s Department of Corrections has offered little explanation about the lockdown or why it has lasted so long.

“There were multiple threats of disruption and assaultive behavior toward staff or other persons in our care, but there was not one specific incident that prompted the facility to go into modified movement,” said Kevin Hoffman, the department’s deputy director of communications. According to state data, nearly 100 assaults have occurred there in the past fiscal year.

Others familiar with the sprawling penitentiary suggest another reason for the restrictions: dire staffing shortages.

More than half of the prison’s 284 full-time positions for correctional officers and sergeants remain unfilled, state data shows. The shortages have severely hobbled the facility’s ability to operate safely, according to former wardens, correctional officers and members of Waupun prison’s community board.

“If I was the warden right now, I’d have that institution on lockdown, too,” said Mike Thurmer, who once ran the prison and now sits on its community relations board. “You can’t have a 40 or 50 percent vacancy rate and not have at the very minimum a modified lockdown.”

What is happening in Waupun illustrates a reality at prisons across the country: Lockdowns, once a rare action taken in a crisis, are becoming a common way to deal with chronic staffing and budget shortages.

Critics say these shutdowns became easier to justify during the pandemic, when prison officials could cite the need to control the spread of the Covid. But even as most Covid-related restrictions have been lifted, lockdowns continue to be applied.

“They are using it at the drop of a hat because it makes day to day operations easier,” said Tammie Gregg, deputy director for the A.C.L.U.’s National Prison Project.