Artificial light disrupts sex hormones of birds

http://www.environmentalhealthnews.org/ehs/news/2014/aug/wingedwarnings6lossofnight

By Jane Kay
Environmental Health News
Sept. 4, 2014

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Around the world, scientists seeking to answer that question have gathered mounting evidence that city lights are altering the basic physiology of urban birds, suppressing their estrogen and testosterone and changing their singing, mating and feeding behaviors. One lab experiment showed that male blackbirds did not develop reproductive organs during the second year of exposure to continuous light at night.

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Streetlights, shopping centers, stadiums and houses turn night into day, a phenomenon that scientists call “loss of night.”

“Birds are particularly sensitive to light and different chemical interventions. If you see these deleterious effects in the birds, you’re likely to see them in humans in short-order. The smart thing to do is to pay attention to avian life,” said Vincent Cassone, whose University of Kentucky lab examines neuroendocrine systems of birds and mammals.

People can suffer an array of health problems when they work night shifts that alter their circadian, or daily, cycles governed by a biological clock. In the wild, light pollution causes hatchling sea turtles to lose their way from beach to the ocean, and disorients Monarch butterflies searching for migration routes. In field experiments, Atlantic salmon swim at odd times, and frogs stop mating under skies glowing from stadium lights at football games. Millions of birds die from collisions with brightly lit communication towers, and migratory flocks are confused by signals gone awry.

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“There might be a physiological or biomedical cost. With humans, we are starting to realize that disrupting body clocks can really come with serious health consequences linked to immune function, metabolism, cancer, obesity and diabetes. These types of things are relatively unexplored in wild animals," Dominoni said.

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Two-thirds of the world, and 99 percent of the United States’ lower 48 and the European Union, live under conditions of light pollution. City lights can outshine natural night sky by 4.8 times, according to European scientists. In Vienna and Plymouth, England, the natural cycles of moon brightness are close to extinct.

In 2001, scientists reported that one-fifth of the world population, and more than two-thirds of the U.S. population, can’t see the Milky Way with the naked eye

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