A statement from the band's management company, Vector Management, said bassist Jared Followill seemed to be a particular target of the pigeons, whose droppings were a potential health hazard.
"I'm surprised they stayed on for as many songs as they did," Andy Mendelsohn of Vector Management said in the statement. "Jared was hit several times during the first two songs. On the third song, when he was hit in the cheek and some of it landed near his mouth, they couldn't take it any longer.
"It's not only disgusting -- it's a toxic health hazard," Mendelsohn said. "They really tried to hang in there. We want to apologize to our fans in St. Louis and will be back as soon as we can."
The crowd grew restless after the band walked off, then an announcement was made that the show was over for "safety reasons." The concert promoter, Live Nation, did not respond to interview requests on Monday but said fans will get a full refund.
Mendelsohn said band representatives had been warned of a "significant" pigeon infestation in the rafters, but were told efforts were being made to correct the problem.
The opening bands, The Postelles and The Stills, performed and were apparently hit with their share of droppings too.
"We couldn't believe what The Postelles and The Stills looked like after their sets," Followill said in the statement. "We didn't want to cancel the show, so we went for it. We tried to play. It was ridiculous."
Health experts say pigeon droppings have been associated with three diseases: Histoplasmosis, cryptococcosis and psittacosis. Histoplasmosis and cryptococcosis are fungal diseases with symptoms that can include fatigue and fever. Psittacosis is a rare infectious disease characterized by fever, rash, chills, headache and sometimes pneumonia. Only about 50 cases of psittacosis in the U.S. are reported annually.
The Kings of Leon performed Saturday night in Chicago. Their tour was continuing Monday in Cleveland and Wednesday in Toronto.
The venue in Maryland Heights, Mo., had another infamous incident nearly two decades ago. In July 1991, Guns N' Roses frontman Axl Rose became enraged when a concertgoer was spotted filming the show. Rose jumped into the audience and tackled the fan, then returned to the stage, blamed security and said, "I'm going home!"
The abrupt end to that concert set off a riot that left dozens injured. The concertgoer sued Rose, and a settlement was reached after the trial began.