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CHICAGO, Nov.11 (Xinhua) – A University of Michigan (UM) study has suggested that human-caused noise and light pollution can harm individual species of bird populations.
Researchers looked at a large collection of datasets to assess how artificial light and human-caused noise affected the reproductive success of 58,506 nests from 142 bird species across North America. They considered several factors for each nest, including the time of year when breeding occurred and whether at least one chick escaped the nest.
The researchers found that light pollution causes birds to start nesting up to a month earlier than normal in open environments, such as grasslands or wetlands, and 18 days earlier in wooded environments.
The consequence could be a mismatch in timing – hungry chicks may hatch before their food is readily available.
As the planet warms, bird food is available sooner due to the warmer climate. Birds that keep their breeding times historical because their internal clocks are set to changes in the length of the day can survive fewer chicks because the food source they rely on already came and went.
These findings suggest two conclusions about birds’ responses to climate change. First, at least temporarily, birds in artificial lighting conditions could track climate change better than those in dark areas. Second, when scientists thought birds were adapting their breeding times to climate change, the birds may have actually responded to light signals, because many studies have been conducted in areas exposed to some light pollution.
The researchers then delved into the details for 27 bird species. They found that a bird’s ability to see in low light conditions and the tone of its call correlated with the species’ responses to light and noise pollution, respectively.
The more light a bird’s eye can absorb, the more the species has shifted its breeding time to the beginning of the year in response to light pollution and the more it benefited from light pollution with better nest success .
After examining the effects of noise pollution, the researchers found that birds living in wooded environments tended to be more sensitive to noise than birds in open environments.
Noise pollution has delayed the nesting of birds whose songs are at a lower frequency and therefore more difficult to hear through human-caused low-frequency noise. Mating decisions are made based on the male’s song and, in some cases, females need to hear the male’s song to become physically ready to reproduce.
These trait-specific and environment-specific findings have strong implications for wilderness management, according to the researchers.
The study is the first step towards a broader goal of developing a sensitivity index for all North American birds. The index would allow managers and conservationists to cross multiple physical traits of a species to assess how factors such as light and noise pollution would affect each species.
The study is published online Wednesday in the journal Nature. Enditem
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