Leaving your lights on at night might be disrupting birds’ sleeping patterns and affecting their ability to function throughout the day, according to a world-first study looking at wildlife’s neurological responses to light pollution.
Researchers at La Trobe University and University of Melbourne found that both artificial white light, as well as the allegedly more “sleep-friendly” amber light, can disrupt the length, structure and intensity of sleep in pigeons and magpies.
Using miniature sensors to measure the birds’ brain activity, they observed that “when experimentally exposed to light at night at intensities typical of urban areas, domestic pigeons and wild-caught Australian magpies slept less, favoured non-rapid eye movement (NREM) sleep over REM sleep, slept less intensely, and had more fragmented sleep compared to when lights were switched off.”
While both pigeons and magpies typically average about 10 hours of sleep a night, the researchers found that pigeons lost about four hours of sleep when exposed to both white and amber light. For magpies, white light was found to be more disruptive to NREM sleep than amber light—indicating that the severity of the impacts of light pollution on birds’ sleeping habits differs between species.
La Trobe University sleep expert Dr. John Lesku pointed out, however, that “neither species fully recovered sleep lost to white or amber light exposure."
The researchers expressed concern over the findings, suggesting that disrupted sleeping patterns could force birds to catch up on sleep in the daytime and thus impact their ability to forage for food, fight off predators and search for mates.
To help mitigate those impacts, city dwellers are being urged to take local wildlife into consideration when carrying out their own nighttime behaviours.
"We should think about using artificial light only as and where it's needed," said Farley Connelly, a graduate researcher at University of Melbourne and La Trobe University. "Switch off that porch light, install sensor lights, remove decorative lights from trees, balconies and other outdoor settings, and keep street and park lights directed to the ground or shielded where possible.”
As a final note, Connelly adds: “if you're ever woken by the early call of a magpie, remember: it could be just as sleep deprived as you are."