Traffic noise makes rural robins more aggressive

Robins living in rural areas become more physically aggressive when they are enduring traffic noise, according to a new study led by Anglia Ruskin University. For the investigation, the researchers analyzed the behavior of male European robins living in both urban and rural areas.

“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 and this is likely to be the key reason why urban robins are typically more aggressive than rural birds,” explained study senior author Dr. Caglar Akcay.

“It should be stressed that physical aggression is a risky behavior for small birds like robins and is likely to have health consequences.”

 Robins rely on visual and acoustic signals to deter other birds from invading their space. While defending their territory, robins change their songs, display red feathers on their neck, or even attempt to chase off intruders by moving closer to them. 

“Signals are extremely useful because they can deter an intruder without a fight that may be costly to both the territory owner and the intruder, but if the songs can’t be heard by the intruder the robins may have to resort to physical aggression,” said study lead author Çağla Önsal. “However, this not only risks injury but displays of aggression can also draw attention to predators, such as sparrowhawks.”

The team used a 3D model of a robin as a simulated intruder to observe the responses of urban and rural robins. The results showed that urban robins typically displayed more physical aggression than rural robins. 

However, the experts found that rural robins became more aggressive when recordings of traffic noise were played during territorial interactions. The simulated traffic noise did not affect levels of physical aggression in urban robins. 

According to the researchers, urban robins have likely learned to “sit out” temporary increases in traffic noise while rural robins have not. Instead, they compensate with increased physical aggression.

“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,” said study senior author Dr. Caglar Akcay.

“In normally quiet surroundings, we found that additional traffic noise leads to rural robins becoming more physically aggressive, for instance approaching the model bird more closely, and we believe this is because the noise is interfering with their communication.”

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

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By Chrissy Sexton, Earth.com Editor

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