Male Birds in the Galápagos Get More Aggressive When Around Traffic Sounds, New Study Discovers

A certain species of bird in the Galápagos becomes more aggressive when exposed to traffic sounds, according to new research.

A study published in the journal Animal Behaviour states that male Yellow Warblers who live close to roads sing more loudly and frequently when exposed to human traffic noises — which ultimately leads to more physical acts of aggression among the animals.

“Communication usually is in lieu of physical aggression but, if the communication is not possible because of noise, then they might actually engage in risky behaviors that would lead to a physical fight,” Dr. Çağlar Akçay, a co-author of Anglia Ruskin University’s study, told The Guardian.

The authors note that birdsong is often a key component in “agnostic” communication that is related to hierarchy and dominance.

They also note that effective acoustic — or sound-based — forms of communication can prevent physical, more aggressive forms. However, if normal acoustic-based forms of communication go unheard, an animal may need to resort to other means to protect its territory.

The researchers obtained the results of their study by playing two different audio tracks within 38 active Yellow Warbler territories. About half of the Yellow Warblers were exposed to a track that solely featured the sound of other birds, while the other half were exposed to a track that featured both birds and traffic sounds.

Researchers found that the birds that lived close to roads became increasingly aggressive in their communication patterns when exposed to traffic noises — sometimes even physically flying over to the speakers. 

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“If there was an actual bird instead of a speaker, that would mean [...] a challenge, essentially, and that could result in a physical fight,” Akçay told The Guardian. 

He added that these results indicate that we should "think about the effects of noise pollution even in places like [the] Galápagos [...] and the impact of noise pollution on the unique species there.”

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The study additionally discovered that while birds that nested close to roads became more aggressive when exposed to traffic sounds, those that nested far away from traffic became quieter — which researchers said could be because they were fearful of the unfamiliar sounds.

By contrast, the researchers noted that the birds that nested near traffic may have learned that their normal sound levels go unheard in the presence of cars and other vehicles, forcing them to resort to more aggressive tactics.