Authorities said the 35-year-old Sicilian man had several kilos of birdseed and was offering it to tourists in exchange for a "donation" so they could have their pictures taken feeding the city's pigeons, ANSA reported Wednesday.
Seven tourists who had purchased birdseed from the man got written warnings, police said.
"People keep feeding the pigeons despite the fact that we have signs posted in four languages explaining that it is illegal," police said in a statement. "We only fine tourists if they continue to feed them after being warned."
It was unclear how much the man was fined for selling birdseed. Violating the pigeon-feeding ban, which was enacted in April 2008, can lead to a fine of 50 euros (about $86), The Washington Post reported last spring.
The man selling the seed told police he didn't believe he was doing anything wrong.
"It's not like I'm dealing drugs, I'm just trying to make a living," he said. "There's no harm in it."