Light pollution has long been known to disorient nocturnal birds, which use the shine of the moon and stars to navigate. In some instances, light pollution leads to cases of fatal attraction, with reports of confused flocks -- sometimes numbering in the tens of thousands of birds -- crashing into the ground or illuminated smokestacks. And too much night light isn't good for birds' love lives, either, says a group of biologists at the University of Veterinary Medicine in Vienna, Austria.
The Viennese scientists believe that light pollution impacts birds on a local scale. Female blue tits, for example, "tend to be unfaithful to their partners, but do so covertly," states veterinarian Katharina Mahr. But without the cover of night, she says, birds may choose partners differently. Too much light disrupts sleep cycles and circadian rhythms -- and, as Mahr points out, these rhythms influence mate choice.
We need to be more critical with our use of lighting, Mahr and her colleagues say. It's not a problem limited to blue tits, of course, or forests near Vienna -- densely populated cities across the world are light polluters (Hong Kong, for example, is 1,000 times brighter at night than your standard spot on the planet). "Urban planning should take into account the question of where light sources are really necessary." Setting up darker areas, where safe -- and cutting back on light-up billboards and other extraneous illumination -- would be a boon for the birds and other animals.