When the April 2024 "Great American Eclipse" plunged midday into near-night, the daily rhythms and vocal behaviors of many bird species shifted dramatically; some fell silent, others burst into song, and many erupted into a "false dawn chorus" after the Sun returned, singing as if a new day had begun. In a new study, merging citizen science, machine learning, and a continent-wide natural experiment, researchers reveal the immediate effects of light disruption on bird behavior. The daily and seasonal rhythms of birds are tightly governed by shifts between light and dark. But what happens when those cycles are suddenly interrupted, such as during a total solar eclipse? Although past studies have sought to understand the effects of solar eclipses on animal behavior, most have offered only scattered or anecdotal glimpses of how animals respond. Liz Aguilar and colleagues saw the April 2024 total eclipse, which cast nearly 4 minutes of daytime darkness across a large swath of the central and eastern United States, as a rare opportunity to investigate, providing an unprecedented natural experiment in how birds react to abrupt changes in light.
In anticipation of the April 2024 total eclipse, which cast nearly 4 minutes of daytime darkness across a large swath of the central , Aguilar et al. created SolarBird, a smartphone app that allowed users to record bird behavior during the eclipse in real time. Its use by citizen scientists generated nearly 10,000 observations spanning 5,000 kilometers of the eclipse's path. At the same time, Aguiilar et al. deployed autonomous recording units at sites across southern Indiana, which captured ~100,000 bird vocalizations before, during, and after totality. These recordings were analyzed with BirdNET, an AI system capable of identifying species calls and quantifying vocal activity. According to the findings, of 52 species detected, 29 showed significant changes in their vocal behavior at some point during the event, yet the eclipse did not affect all species equally. In the minutes leading up to totality, 11 species sang more than usual as the sky darkened. During the four minutes of darkness, 12 species responded, with some falling silent while others grew more active. The strongest reactions came after the Sun returned, when 19 species changed their songs in what resembled a false dawn chorus. Barred owls called four times more often than usual, while robins – who are well known for their pre-dawn songs – sang at six times their usual rate. According to Aguilar et al., these patterns suggest that the eclipse temporarily reset some birds' biological clocks, prompting them to behave as though a new day had just begun.
For reporters interested in trends, an August 2025 Science Research Article shows how light pollution has affected the vocal behavior of birds. According to the findings of Brent Pease et al., birds were generally vocal for nearly an hour longer when in the presence of light pollution, particularly for species with large eyes, open nests, migratory habits, and large ranges and during the breeding season.
Podcast: A segment of Science's weekly podcast with Liz Aguilar and Kimberly Rosvall, related to this research, will be available on the Science.org podcast landing page after the embargo lifts. Reporters are free to make use of the segments for broadcast purposes and/or quote from them – with appropriate attribution (i.e., cite "Science podcast"). Please note that the file itself should not be posted to any other Web site.
