Fires started by carelessly discarded cigarettes are nothing new to the London Fire Brigade—but the culprits are usually people, not birds. Investigators were initially baffled by a fire on the roof of a building in south London, but they eventually concluded that it had been started by a lit cigarette carried to the rooftop by a bird, the BBC reports.
"No one had been up to there for a long time and there were no electrics that could have sparked a blaze," an investigator writes at the brigade's website. "We looked everywhere, but the smoking gun was found when we discovered a partially burnt birds nest. Neighbors told us they often saw birds flying in and out of a hole in the roof. We believe that one of the birds picked up a cigarette butt that was still smoldering and dropped it into the nest, causing it to catch fire and set the roof alight."