Authorities in Rome have enlisted falcons to scare off defecating starlings, as the Italian capital plays host to a growing menagerie of animals, including gulls, wild boars and sheep.

Starlings pass through the city in late autumn as they migrate to warmer climes for winter, soiling its cobblestones and riverbanks with sticky guano and bothering residents and tourists, who often use umbrellas to avoid the droppings.

Part of the road that runs along the Tiber River was closed earlier this week because the birds had left so much excrement, prompting authorities to call on a team of falconers. It is unclear when the birds of prey will take to the skies, but their job will be to frighten the starlings away from their nesting spots, such as the trees along the streets.

The Rome department in charge of environmental sustainability said the measure constituted a “cruelty-free, ecological and natural solution” to the starling problem.

Animal rights activists condemned the initiative as “barbaric”. “The environmental sustainability council says that using hawks to fight starlings is ‘cruelty-free, ecological and natural’ – these are shameful words that justify what is a cruel and anachronistic method,” said Rinaldo Sidoli, a communication manager for Animalisti Italiani.

He added that the deterrent violated a municipal rule which prohibits the “release into the environment of birds, except those treated by authorised wild animal recovery centres”.

An initiative involving falcons in 2015 also drew criticism. Previous city authorities experimented with playing recordings of starling distress calls in an attempt to get the birds, who tend to descend on the city at dusk, to flee.

The arrival of the falcons will add to what Romans have started to describe as the city’s “zoo”. Despite being about 19 miles (30km) from the coast, the gull population has grown as the birds scavenge for food waste in the historical centre, while wild boars have also been spotted rummaging through piles of rubbish in areas beyond.

In May, the city’s administration, which since June 2016 has been led by the anti-establishment Five Star Movement, the party governing at national level with the far-right League, said it would use sheep and other animals to tackle overgrown grass in parks.

The cash-strapped administration faces myriad woes, including waste collection, potholes and an inefficient public transport system. In October, thousands of residents protested against what they called the city’s “degradation”.