While frequently overlooked, noise pollution is one of the biggest problems in city life. Studies have shown we all get more aggressive when exposed to loud noises, such as traffic jams, with plenty of angry drivers. And it’s an issue that goes much beyond humans, according to a new study, which found birds can get more violent too.

Researchers from Anglia Ruskin University in the UK and Koç University in Turkey found that human-made noise pollution causes European robins (Erithacus rubecula) living in rural areas to become more physically aggressive. This builds into previous studies that found that robins living in cities were more aggressive than their rural cousins.

Beloved for their sweet song and plump appearance, robins are actually very competitive creatures. Their calls and behaviors are part of a struggle for territorial dominance over their neighbors. When a robin arrives uninvited on another bird’s territory, they change their songs and adopt visual displays to ward the rival away.

“We know that human activity can have a significant impact on the long-term social behaviour of wildlife, and our results show that human-produced noise can have a range of effects on robins, depending on the habitat they live in,” Caglar Akcay, researcher at Anglia Ruskin and senior author of the study, said in a statement.

Robins and noise pollution

To explore the connection with noise, the researchers placed a 3D-printed plastic model of a robin on another robin’s territory at two locations: an urban park in Istanbul close to a road and a quiet wooded area outside the city. The model was equipped with recordings of robin songs. Then, via a speaker, the researchers added traffic noise.

Our new preprint led by @cagla_onsal is online: Aggression and multimodal signaling in noise in the European robin https://t.co/r3Bb4H3WyX @ekoevoder
supported by @IBIS_journal small ornithological grant to Çağla. (1/4) pic.twitter.com/TclzcApSeA

— Çağlar Akçay (@caglarbakcay) May 3, 2022

The researchers found urban robins displayed more physical aggression than rural ones. However, rural robins became more aggressive when adding the traffic noise. This is likely because of the noise interfering with the songs used by the birds to display territoriality. Urban robins likely got used to the noise, while rural ones didn’t, the team believes.

“The chronic high levels of noise that exist day and night in urban habitats, such as from traffic or construction equipment, may permanently interfere with the efficient transmission of acoustic signals,” Akcay said in a media statement. “This is likely to be the key reason why urban robins are typically more aggressive than rural birds.”

Being more aggressive is likely making these birds’ lives more difficult, the researchers said. For example, if they make more of a scene when a rival gets in their territory they could then become more vulnerable to predators, especially when their attention was focused on a rival – not being able to fly away or run away fast enough to protect themselves.

The study was published in the journal Behavioral Ecology and Sociobiology.