Light, noise pollution helps some birds adjust to climate change

December 23, 2020

A bird feeds one of its young in an area near street lamps. (Ezra Jeffrey, Unsplash)

Some birds with strong night vision may have been able to adapt to climate change more effectively by nesting earlier in the season, and using highly lit areas for breeding activities, according to a new paper published in Nature.

A team of scientists analyzed more than 58,000 observations of nests from 142 bird species across the contiguous U.S., comparing them against data on light and noise pollution to see how they affected the survival rates. These sensory pollutants have previously been shown to disturb reproductive, migratory and other behaviors in a range of animals.

Researchers found that birds living near a lot of light pollution nested as much as a month earlier than in darker regions, which they expected to reduce breeding success by misaligning the birds with the time food is most plentiful. But the team was surprised to find that birds that see well in low-light conditions had more of their young leave the nest.

The study didn’t capture why these birds benefited from light pollution, said Clinton Francis, a professor of biological sciences at California Polytechnic State Institute and the study’s senior author. But they bring up “intriguing possibilities.” The birds with good low-light vision may be able to forage more at night, or earlier nesting may realign them with environments already disrupted by the warming climate.

“If climate change is causing their food to peak earlier in the season, light pollution might actually be helping them realign that timing, or restore that timing,” Francis said.

Many other birds in the study, however, were found to suffer when near light and noise pollution, which can confuse their internal clocks and drown out mating calls. Forest-dwelling birds were the most disrupted by noise, which was also unexpected because forests dampen sounds more than “open habitats” such as grasslands and wetlands.

The authors had trouble explaining the trend, but suggested it was because forest inhabitants evolve lower-pitched calls to reverberate through densely packed plants but are interrupted by the low-frequency sounds of human activity. Francis calls the hypothesis “weak,” however, because the breeding trend held for both small and large birds, which respectively have high- and low-pitch mating calls.

The bird-nest data came from NestWatch, a citizen-science program managed by Cornell University that monitors bird nests in the U.S. that provided records on bird reproduction from between 2000 and 2014. Francis and his team also used noise data from the National Park Service, as well measurements of nighttime artificial light taken from a satellite operated by the National Oceanic and Atmospheric Administration.

Francis said the study is valuable for its new insights into the effects of human activity on bird populations, but that it only captures a few factors of the phenomenon. He said more research needs to be done on the vision and hearing abilities of birds and how they affect the animals’ responses to sensory pollution and other environmental conditions, which could possibly create evolutionary changes within the animals.

Reducing noise pollution to avoid drowning out birds would also benefit humans, who experience greater “restorative effects” when they hear bird songs, according to a recent study that Francis also worked on. Furthermore, traffic noise alone takes millions of years off of the lives of the world population each year by disturbing sleep, increasing stress and worsening cardiovascular and other health issues.

Similar issues are tied to light pollution, which afflicts more than 99% of U.S. and European populations as well as more than 80% of the world. Animals ranging from birds to turtles to insects are disoriented by bright lights at night and have their survival threatened, and humans may be at higher risk of diseases such as cancers, obesity and Type 2 diabetes when their sleep and circadian clock are disturbed by light pollution.

Francis said there are many ways that people can help birds and each other by reducing sensory pollution. He recommended buying tires with better noise ratings, foregoing leaf blowers and buying fixtures that inhibit light from escaping into the night sky.

“With sensory pollutants, there's actually a lot that individuals can do,” the senior author said. “Even smaller scale local governments can make a really big difference for wildlife and for people.”

The article, “Sensory pollutants alter bird phenology and fitness across a continent” was published Nov. 11 in Nature.

The authors of the study were Masayuki Senzaki, Jennifer Phillips, Ashley Wilson and Clinton Francis, California Polytechnic State University; Jesse Barber and Christopher McClure, Boise State University; Neil Carter and Mark Ditmer, University of Michigan; Caren Cooper and Jelena Vukomanovic, North Carolina State University; Kurt Fristrup, National Park Service; Daniel Mennitt, Exponent; and Luke Tyrrell, State University of New York Plattsburgh. The lead author was Masayuki Senzaki.

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