A recent study found that birds that live closer to roads display more aggression than birds of the same species that live farther away from noisy vehicles, Mongabay’s Spoorthy Raman reported.
Researchers looked at the behavioral differences of male Galápagos yellow warblers (Setophaga petechia aureola) on two islands of the Galápagos, an Ecuadorian archipelago in the Pacific Ocean known for its rich biodiversity.
Within known territories of 38 male yellow warblers on the islands, the researchers played prerecorded songs of an intruding warbler on a speaker. To some recordings, they had added traffic noises, while the others only had warbler calls. Male yellow warblers tend to shoo away other males that wander into their territory with songs.
On both islands, the researchers found the same pattern in response: Male birds that lived closer to the roads were more aggressive when the speaker played recordings of an intruding bird’s song with added traffic noise than those that lived far away from roads.
The birds living closer to roads circled the speaker in closer proximity, rather than simply singing — behavior associated with aggression and higher risk of physical conflict.
The birds also increased the lower-pitched noises in their song, presumably to be heard over the traffic noise, while those living far from the roads sang in higher pitches.
“Many species may adjust their behaviors and be able to live near noise, but the most sensitive species are likely not able to change their behaviors or deal with the stress of daily noise interruptions,” Jennifer Phillips, a bioacoustics researcher from Washington State University, U.S., who was not involved in the study, told Raman by email.
“This is why cities or human impacted areas often have lower biodiversity, because more sensitive species are the first to go,” she added.
The researchers ran the trials on two very different Galápagos islands. Santa Cruz Island, the Galápagos’ most populated island, has around 15,000 residents, about 15,000 yearly tourists and an estimated 1,000 vehicles. Meanwhile, Floreana Island has a human population of around 100 and just 10 cars. The researchers found that even lower amounts of traffic were enough to cause a change in behavior.
The human population of the Galápagos has increased tenfold in the last 50 years, and the numbers of cars has followed the trend.
“We’ll see more and more effects of this as humans alter the habitats,” said study co-author Çağlar Akçay, a behavioral ecologist at Anglia Ruskin University, U.K. “There [are] very few places on Earth where there’s no human noise.”
Read the full story by Spoorthy Raman here.
Banner image: A pair of Galápagos yellow warblers. Image courtesy of Çağlar Akçay.
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