Scientists from Southern Illinois University and Oklahoma State University analysed 2.6 million instances of singing by 583 bird species using data from the BirdWeather project. They found that in areas with high levels of light pollution, birds sing on average 50 minutes longer, starting 18 minutes earlier and ending 32 minutes later than in dark areas.
Light pollution has the greatest impact on species with large eyes, open nests and extensive ranges, especially during the breeding season. Scientists have not yet determined whether this change is positive or negative for bird health: additional activity may interfere with rest, but at the same time increase the time available for foraging and improve reproductive opportunities.
Researchers estimate that 80% of life on Earth is exposed to light pollution, which is already affecting the nocturnal migrations of birds, seasonal hormonal rhythms, and the reproductive functions of other animals, including sea turtles.
The authors of the study emphasise that restoring the natural darkness of the night requires global cooperation and could become a key focus of nature conservation in the 21st century.
