UPDATE (10/23/19, 4:25 PM) Otte says he misspoke and 100 pigeons can produce 4,000 of waste "annually".
The city of San Luis Obispo is putting the birds downtown on birth control.
It's an initiative to try to solve several environmental problems downtown.
It all starts with the water quality of the creek that runs alongside Mission Plaza.
The Central Coast Regional Water Quality Control Board has determined the water is so contaminated with fecal matter, the city has to do something about it to prevent people from getting sick with E. Coli and other viruses.
The city believes the birds are to blame for this constant contamination.
In a tunnel alongside Mission Plaza, hundreds of pigeons have created their own sanctuary.
"So we have a very robust pigeon population that lives in the tunnel, upwards of about 500 birds. If you think of a flock of 100 birds being able to produce 4000 pounds of poop every day, multiply that by five and you have a lot of pigeon poop going into the creek every day," explained city of San Luis Obispo Biologist, Freddy Otte.
The Central Coast Regional Water Quality Control Board has cited the city for unhealthy levels of fecal bacteria in the creek.
"With their tests they discovered that there was a spike in fecal coliform here in Mission Plaza so they think it was potentially human related or bird related - anything like that. So we have dove in deeper to discover what's actually in the water," Otte said.
Part of that plan includes putting the birds on birth control as fewer birds means less bird poop. The city has spent time training the birds to eat from feeders downtown that have birth control in the food.
"An urban pigeon lives for about 2 or 3 years. If you think about the conditions (in the tunnel), the pigeons aren't going to survive very long as opposed to somewhere that's more conducive to them that's got good habit, good feed, not dirty, filthy conditions like in the tunnel," Otte said.
The city believes less bird poop will also mean fewer flies, something many downtown shoppers are frustrated with.
"It's super gross when you're walking by, trying to look into a store and flies are all in your face and you have to swat them away," said shopper Ali Coine.
"It's kind of petrifying at first especially when you have food and they come and attack and you don't want to eat because it's really nasty," said shopper Aman Thandi.
"So by reducing the pigeon population we're hopefully going to clean up not only the creek system, but also the habitat in the tunnel to have less breeding opportunities for the flies as well," Otte said.
The city says they met with several animal rights activists groups including PETA and California Fish and Wildlife before putting the birds on the birth control.
They plan to check back every six months to see how the population is changing, with hopes of having an 80 percent reduction in birds in 18-24 months.
The city says they also are working alongside Cal Poly to develop a spray for parts of downtown to help mitigate the flies as well.