Noise and light pollution alter the breeding behavior of birds

Noise and light pollution have substantial impacts on the timing of breeding among birds,  which can compromise their reproductive success. These impacts were largely overlooked until recently, when a collection of studies revealed how individual bird species are affected by noise and artificial light. A new study from California Polytechnic State University is the first to describe the detrimental influence of sensory pollution on bird species worldwide.

“Our study provides the most comprehensive evidence that noise and light can profoundly alter reproduction of birds, even when accounting for other aspects of human activities,” said study co-lead author Clint Francis.

Over the last few decades, bird populations have dropped by more than 30 percent. Experts are scrambling to understand what is contributing to these large declines, so that the trend may be reversed. The new findings suggest that noise and light pollution must be classified among the environmental factors that are causing birds to disappear at such a shocking rate.

The investigation was focused on a massive collection of datasets, including data collected by citizen scientists through the NestWatch Program. The researchers assessed how light and noise pollution affected the reproductive success of 58,506 nests from 142 species across North America. 

The study revealed that light pollution causes birds to begin nesting up to a month earlier, and this shift in reproductive timing can cause the chicks to hatch before enough food is available. The consequences are made even more complex by climate change.

Global warming is causing spring greening to occur earlier, and insects are hatching earlier to keep pace. This means that the historical reproductive timing of birds may no longer coincide with peak food availability.

“We discovered that the birds that advanced the timing of their reproduction in response to increased light pollution actually have better reproductive success,” said Francis. “A likely interpretation of this response is that light pollution actually allows these birds to ‘catch up’ to the shift towards earlier availability of food due to climate change.”

According to the researchers, birds in areas impacted by light pollution may track climate change better than those in in natural habitats that are darker – at least temporarily. 

Overall, the experts determined that a bird’s ability to see in low light and the pitch of its call were related to responses to light and noise pollution. For example, the more light a bird’s eye is capable of taking in, the more likely it is that the species will move its breeding time earlier in the year in response to light pollution. 

Noise pollution was found to delay nesting for birds with songs at a lower frequency due to the interference of low-frequency human noise. These songs are critically important for mating interactions. The study also showed that exposure to noise pollution was more disruptive to birds living in forested environments compared to birds in open environments.

“We show convincingly across a lot of species that noise and light pollution are having strong effects on wild populations,” said Francis. “If there’s a proposed development and land managers are worried about a bird that they have no information on, they can use this study to see whether the development is likely to affect the bird. Is it a forest bird? If so, it is likely that it is more sensitive to light and noise.”

The study is published in the journal Nature.

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By Chrissy Sexton, Earth.com Staff Writer