A sudden, midday twilight threw the rhythms of North American birds into disarray during the total solar eclipse of April 8, 2024, prompting widespread and sometimes contradictory changes in behavior. For a few minutes, as the moon obscured the sun, birds across the continent reacted to the unexpected darkness, with many falling silent while others increased their calls. The fleeting event provided a rare opportunity for scientific observation, revealing just how deeply solar cues govern avian life.
This massive natural experiment was captured by thousands of ordinary people in an unprecedented citizen science effort. Armed with smartphones and dedicated audio recorders, volunteers from Mexico to Canada collected a treasure trove of observational and acoustic data. Subsequent analysis, powered by artificial intelligence, showed that more than half of the studied species significantly altered their behavior, with many bursting into a “dawn chorus” as the sun reappeared. The findings demonstrate the profound power of light in structuring the daily lives of animals and highlight the growing role of public participation in large-scale ecological research.
A Continent-Spanning Laboratory
The study harnessed the public’s fascination with the eclipse to build a vast observational network. Two primary methods were used to gather information across the path of totality. The first, a smartphone application called SolarBird, allowed users to log specific behaviors. A total of 1,174 participants submitted 6,951 individual 30-second observations, noting activities like singing, flying, or foraging. The app automatically recorded the precise time and GPS coordinates, allowing researchers to correlate the behaviors with the exact degree of sun obscuration at that location.
In parallel, the NASA-supported Eclipse Soundscapes project collected an enormous acoustic dataset. This initiative equipped citizen scientists with 383 autonomous recording units. These devices were set up in natural environments to capture the ambient soundscape for two days before and two days after the eclipse, providing a crucial baseline for comparison. The effort yielded an immense 45,960 hours of audio, totaling 25 terabytes of data, offering an unfiltered auditory record of how birds and other animals responded to the celestial event.
The Unnatural Nightfall
As the moon’s shadow passed, the data revealed a significant disruption to the birds’ established daily cycles. The brief plunge into darkness triggered behaviors typically associated with dusk and dawn, but in a compressed and unusual sequence. Analysis of the combined data showed that 29 of 52 identified bird species—more than half—were significantly affected by the eclipse at some stage. The overall volume of bird vocalizations during the eclipse afternoon was 20% to 50% higher than during the same time window on the days before and after the event.
Vocalizations in Flux
The acoustic recordings captured the most dramatic effects. In the minutes leading up to totality, 11 species began to vocalize at higher-than-usual rates, as if beginning an evening chorus. When the sun was fully obscured, the response was split: 12 species showed unusual vocalization patterns, with half increasing their calls and the other half falling silent. This suggests that different species interpret the sudden darkness in different ways, with some treating it as a signal to roost and others perhaps reacting with confusion or alarm. As sunlight returned, many species began singing with renewed vigor, producing a phenomenon researchers described as a reprise of the dawn chorus.
Actions in the Darkness
Observations submitted through the SolarBird app complemented the acoustic data, providing a more complete picture of bird activity. Users reported a general decrease in typical daytime behaviors such as flying and foraging during the eclipse’s peak. Instead, birds were more likely to be recorded as stationary. This aligns with the hypothesis that many diurnal birds interpreted the rapid onset of darkness as nightfall, beginning their transition toward roosting and a state of rest. The combination of increased stationary behavior and altered vocalizations paints a clear picture of a continent of birds momentarily thrown off their natural rhythm.
Artificial Intelligence as Analyst
The sheer volume of data, particularly the 25 terabytes of audio from the Eclipse Soundscapes project, would have been impossible for researchers to analyze manually. To overcome this challenge, the team employed a sophisticated deep neural network called BirdNET. This AI tool was trained to recognize the distinct calls and songs of more than 6,000 species. By feeding the tens of thousands of hours of audio into the network, scientists could automatically identify which species were present and quantify their vocalization rates with high confidence.
During the core 124-minute period surrounding the eclipse, BirdNET identified 15,606 distinct vocalizations from 52 different species in the study area. This automated analysis allowed researchers to move beyond anecdotal accounts, which have characterized studies of past eclipses, and perform a robust statistical analysis. The use of AI transformed the raw data from thousands of volunteers into a coherent and quantifiable scientific result, marking a significant step forward for technology-enabled citizen science.
Understanding Light’s Deep Influence
The 2024 eclipse served as a powerful natural experiment, confirming that light is the primary cue structuring the circadian rhythms of most organisms. Because a total solar eclipse happens in any given location only once every few hundred years, the birds observed had no prior experience with such an event. Their strong, instinctual reactions to just four minutes of unexpected night demonstrate how deeply ingrained these light-driven behaviors are. The study effectively “switched off the sun” in the middle of a spring afternoon, showing that even a very brief interruption of the normal light-dark cycle is enough to disrupt entrained biological rhythms for a majority of wild bird species.
The Path Forward
Researchers emphasize that these findings, while compelling, are still in their early stages. Brent Pease, a subject matter expert involved in analyzing the audio data, noted that the results are preliminary and that much more analysis is needed. The research appeared on the preprint server bioRxiv, indicating it has not yet completed the formal peer-review process.
Future analysis will seek to answer more nuanced questions. Scientists want to determine how close birds needed to be to the path of totality to show a behavioral change and to more closely examine the species-specific vocalizations that made up the post-eclipse “dawn chorus.” Nonetheless, the project has already succeeded in demonstrating the immense potential of combining citizen science, artificial intelligence, and rare natural events to generate new insights into the animal world.