Traffic Noise May Be Making These Bright Yellow Birds More Aggressive in the Galpagos Islands, Study SuggestsMale Galpagos yellow warblers appear to be shifting their behavior and adjusting their calls in response to the din of passing vehicles The Galpagos yellow warbler is a genetically distinct subspecies of the yellow warbler, which might be familiar to residents of the United States. Alper YelimliesThe Galpagos Islands are famous for their pristine, natural ecosystems. But even on this remote and mostly undeveloped archipelago, human activity is affecting animals.Researchers recently discovered that traffic noise may be causing male Galpagos yellow warblers to behave more aggressively when defending their territories. Even exposure to just a handful of cars on a regular basis changed the birds habits, according to a new paper published last week in the journal Animal Behaviour.For the study, scientists focused on the Galpagos yellow warbler (Setophaga petechia aureola), a small songbird thats endemic to the archipelago. The Galpagos Islands, which famously inspired British naturalist Charles Darwins theory of evolution, are located roughly 600 miles off the coast of mainland Ecuador, in the Pacific Ocean.Males have bright yellow feathers covering most of their bodies, with a reddish-brown cap atop their heads during the breeding season. They are territorial birds that defend their turf from other males. Typically, males will sing loudly to warn approaching intruders to stay away. But, if necessary, they will engage in physical fights.Birds use song during territorial defense as an aggressive signal, study co-author alar Akay, an ecologist at Anglia Ruskin University in England, says in a statement. He and his team wondered whether traffic noise might be affecting the birds interactions. If external noise such as traffic interferes with the signaling, effectively blocking this communication channel, increasing physical aggression would be an appropriate response.Traffic noise and bird songWatch on To test this, they visited 38 yellow warbler nesting sites on two different islands: Santa Cruz Island, which has more than 15,000 human residents and more than 1,000 cars, and Floreana Island, which has less than 100 human residents and approximately ten cars. Some of the nesting sites were near roads (within 164 feet), while others were farther afield (more than 328 feet away).At each site, they played two different types of audio recordings: one with the sound of a male Galpagos yellow warbler and traffic noises, and another with only the male bird call, unobscured by the sound of cars. Then, they watched to see how the birds responded.The male Galpagos yellow warblers that lived near roads on both islands reacted more aggressively when they heard the recording of the intruding male alongside traffic. They approached the speaker and repeatedly flew by itwhich researchers used as a proxy for physical aggression. The birds that did not live near roads, by contrast, behaved less aggressively when they heard the recording of the intruder and traffic noises.Its possible that the birds were flying closer to the speaker simply to make themselves heard over the din of traffic. But the males didnt always sing as they approached.And, even if the birds were flying closer simply to talk it out with the intruder, they might still be putting themselves in harms way, says Akay to the London Times Akshay Raja.Getting closer might be interpreted as an aggressive signal, he adds. If youre flying back and forth to defend your territory, some of these birds will have territories on either side of the roads, so they will actually have to fly over the road and they get killed by the vehicles.Indeed, the studys authors note that the Galpagos yellow warbler is the most commonly killed bird on Santa Cruz Islands main road. Galpagos yellow warblers are endemic to theGalpagos Islands. alar Akay / Anglia Ruskin UniversityResearchers noticed other changes in the birds behavior, which they call behavioral flexibility. Male birds increased the minimum frequencies of their songs when they heard the recordings that contained traffic sounds, regardless of where they lived. They likely made this change so their vocalizations did not overlap with the low-frequency vehicle sounds, the scientists suggest.The birds on Santa Cruz Island sang for longer durations when they heard the traffic noise recordings, while the birds on Floreana Island sang for shorter durations. Birds that lived far from roads on both islands also increased the peak frequency of their vocalizations.These findings suggest the birds are trying to cope with the road noise by adjusting their song, even on the sparsely populated Floreana Island, per the study. The team hopes future conservation efforts will include strategies for mitigating noise pollution, which seems to affect wildlife behavior even in relatively remote destinations.Even that little experience [of traffic on Floreana Island], apparently, has some effect, Akay tells the Guardians Nicola Davis. We have to think about noise pollution even in places like Galpagos, I think, and the impact of noise pollution on the unique species there.Get the latest stories in your inbox every weekday.Filed Under: Animals, Biology, Birds, Cars, Charles Darwin, Conservation, Ecology, Ecuador, Evolution, Land Birds, New Research, Wildlife, Zoology