Stars die and vanish from sight all the time, but astronomers were puzzled when one that had been stable for more than a decade almost disappeared for eight months. 

Light pollution is causing birds around the world to sing for longer each day, prolonging their vocalizations on average by 50 minutes, according to a new study by Brent Pease and Neil Gilbert. In their analysis of more than 500 diurnal bird species, they also note that birds that are more exposed to light – whether through large eyes or open nests – are the most affected by light pollution in this manner. Scientists know that light pollution, which impacts 23% of the planet, is influencing activity patterns governed by the circadian light-dark cycle in individual species. The new study is first to document this phenomenon in birds across species and space and seasons. It’s unclear whether these impacts are positive, negative, or neutral for the birds’ fitness, but “documenting these fitness effects and curbing light pollution are challenges for 21st-century conservation,” the authors write. Pease and Gilbert analyzed 2.6 million observations of onset (morning) bird vocalization and 1.8 million observations of cessation (evening) bird calls. The data come from the BirdWeather project, which includes volunteer scientist recordings, automated biodiversity monitoring and machine learning. The researchers found limited evidence for the effects of habitat density, latitude and specific richness on light pollution’s interaction with vocalizations, but they note that their database remains too incomplete for some regions and species to definitively measure these effects.