Gladys Rivera (C) checked to see if there is any coffee left to hand out to the homeless in Franklin Square on December 25. Rivera and members of the Church of God Fountain of Light in Manassas and Windchester, Va. distributed 85 tamales, 85 lunch bags, coffee and bottles of water . (Mark Gail/THE WASHINGTON POST)

Sunday services were starting in 15 minutes at Capitol Hill Presbyterian Church, and Pastor Andrew Walton was alone in the carpeted common area, marking up a program with a highlighter. At this time of the week, the space is normally a crazy intersection of kids and adults.

But this was Christmas. The only sounds in the room were the hum of a coffee maker and the organist practicing upstairs.

“The staff is on vacation, and we wanted to give families some time at home,” Walton said, explaining why the typical schedule had been altered. With Sunday School canceled and a small crowd expected at the 11 a.m. service, Walton jettisoned his sermon and asked congregants to share stories.

Smaller Sunday crowds on Christmas? Seems counterintuitive. But the confluence of the celebration of Jesus Christ’s birth with the conventional church-going day actually proved a conundrum for many pastors.

A new poll by LifeWay Research shows that about 10 percent of U.S. Protestant pastors canceled Sunday services this Christmas. Many others had abbreviated or altered services. Some said they would use the smaller crowds to give their second-string clergy a chance to practice.

Part of the explanation is simple: Christmas in the United States has become a cultural event about food, family and gifts. People are busy, and Christmas is one of the few days of the year when it’s considered legitimate to huddle inside with the snacks, people and devices you love.

“We had about half our usual crowd. A lot of people came last night. They felt, ‘I’ve done my duty,’ ” Randall Balmer, a historian of American religion and an Episcopal priest in Connecticut, said Sunday as he drove home from services. “I feel the pressure myself. I have two of my [grown] kids at home, and I hardly see them.”

The trends are complex. Large swaths of American Christian churches, particularly evangelical ones, don’t hold Christmas Day services — Sunday or not. Requiring church on a family day has been seen as too legalistic, too liturgical, more about an institution than about God.

Historically, this was partly about distinguishing evangelicals from Catholics, Balmer said.

“You have this aversion to calendric observance because it’s seen as too Catholic,” he said. “Evangelicals think it imposes too much structure.”

In some places, the routine of Sunday church held sway.

Walton’s church typically doesn’t hold services on Christmas Day. It only did so this time, for a smaller crowd, because it was a Sunday.

The Christmas-Sunday collision tests another trend: the weakened hold of organized religion. Recent surveys show that the number of Americans who say they are not affiliated with any religious denomination is growing fast. Experts say that it doesn’t necessarily mean people are less spiritual but that they are less tied to a particular church and its schedule.

Some pastors canceled Christmas Day services and instead encouraged congregants to do community service. Megapastor Rick Warren canceled regular services during the Dec. 11 weekend to encourage people to do “Christmas season” projects in the California region where Warren’s 20,000-member Saddleback Church is located.

St. Mark’s Episcopal Church on Capitol Hill combined its two typical Sunday morning services into one. Minutes before the 10 a.m. service, fewer than 20 people were spread out in the huge open brick nave, a space where about 900 people had attended two services the night before. The assistant rector was on the road to Georgia.

Preparing in the back for services, the Rev. Paul R. Abernathy said he appreciated the different vibe on this unusually quiet Christmas.

“There’s an intimacy, less hustle and bustle,” Abernathy said. His sermon for the day focused on Christ’s birth story being about the glory of “self-sacrificial giving, not the glory of political power, or even of nature, or commerce or art.”

Vondell Bethune, 58, typically attends Sunday services at the National Community Church, but the nondenominational D.C. church canceled services for Christmas. Instead, he and other congregants handed out bag lunches to the homeless near Union Station.

“Christmas Day is when you should be with your family,” said Bethune, a landscaper who said that until recently he had been homeless for several years. “Church is the people, the congregation, not the building. . . . Today, we were servants of the Lord, so we did have church.”