A total solar eclipse not only darkens the sky, but also causes animals to "confuse time." On the afternoon of April 8, 2024, as the moon’s shadow swept across the North American continent at thousands of kilometers per hour, a strange thing happened:Thousands of birds suddenly started singing, just like they did in the early morning. At this time, the sky had just plunged into darkness for only a few dozen seconds.

This is no coincidence. During the short four minutes of a total solar eclipse, the physiological systems of many birds were completely deceived - they perceived the sudden darkness as night and the reappearance of light as dawn. So, at the wrong moment, they sang the song of dawn.

This discovery comes from a large-scale study at Indiana University in the United States and was just published in the journal Science.

What’s even more special is that the main force of this research is not scientists in white coats, but more than 1,700 ordinary people scattered along the total solar eclipse observation belt. They used their mobile phones to record the behavioral changes of the birds around them.

Total solar eclipse on April 8, 2024 Source: Photographed by the author

An experiment that required 1,700 pairs of eyes

Ph.D. student Liz Aguilar is well aware of one problem: Scientists can't be in a thousand places at once. A total solar eclipse will not happen again in the same place for 300 to 400 years. If she wanted to take advantage of this opportunity to study the effects of light on wild birds, she needed more eyes and ears.

Thus, a mobile app called SolarBird was born. How to use it couldn't be simpler: Find a bird, observe it for 30 seconds before, during, and after a total solar eclipse, and then check what the bird is doing on the screen—singing, eating, flying, or whatever.

The app automatically records the user's GPS coordinates and calculates the progress of the local eclipse, which is the percentage of the sun that is obscured by the moon. In this way, each observation record accurately corresponds to a specific light change.

The results exceeded all expectations. On the day of the total solar eclipse, the research team received nearly 11,000 observations. The data points follow the path of the total solar eclipse, covering the entire continent from Mazatlan, Mexico, to Newfoundland, Canada.

Aguilar's eyes lit up as he recalled seeing the data for the first time. She insisted that the names of all participants be included in the paper because these people were the true collaborators.

Birds are talking, AI is listening

Meanwhile, another team was doing a more traditional but equally massive job. In the week leading up to the total solar eclipse, researchers deployed dozens of automated recording devices in Bloomington, Indiana, and the surrounding countryside. Each device was about the size of a tissue box, but they recorded a massive amount of bird song.

How to find useful information from hundreds of thousands of birdsong? At this time, artificial intelligence comes on stage.

The research team used an artificial neural network called BirdNET, which is the same technology used by the Merlin recognition application on the phones of many bird watching enthusiasts. The AI ​​scanned all the recordings and identified which birds were chirping at what time. Ultimately, the team analyzed nearly 100,000 recordings of bird vocalizations.

They focused on 52 common species and found that 29 of them had significant changes in their song behavior before and after a total solar eclipse. Many birds that normally sing in large numbers at dawn also burst into song during the total solar eclipse.

Dustin Reichardt, who analyzed the data, put it bluntly: Even a light interruption of just over four minutes can cause dramatic changes in the behavior of birds, especially those species that are accustomed to singing loudly at dawn.

The secret hidden in four minutes

What's really shocking about this study isn't that birds respond to a total solar eclipse - that's not hard to guess. What is truly astonishing is the speed and precision of the response.

Just four minutes. That's how long the total solar eclipse will last in the Bloomington area. In such a short period of time, the physiological systems of many birds not only detect changes in light, but also quickly switch to corresponding behavioral modes. They do not regard darkness simply as some abnormal phenomenon, but as a real signal of the alternation of day and night.


Source: Reference [1]

Project leader Professor Kimberley Rosewall recalled the discovery a year and a half later, her voice still full of wonder: You could turn off the sun, even briefly, and the birds' physiology was so sensitive to this change that they would behave as if morning had come.

The findings point to a larger question: If a four-minute change in light can affect wildlife so profoundly, what are the effects of constant artificial light pollution from urbanization?

City nights are never truly dark. The illumination of street lamps, billboards, and buildings always casts a halo over the city.

For birds whose lives depend on light rhythms, this amounts to a constant disruption of their biological clocks. They may call, feed, or migrate at the wrong times, and these errors ultimately affect their survival and reproduction.

The total solar eclipse became a mirror, allowing us to see a fact that is usually ignored:Light not only allows us to see, it is deeply embedded in the workings of life.

When the public becomes scientists

The study also proves something else: Scientific research doesn't have to be done in a lab or with expensive equipment. Sometimes, an idea, an app, and public enthusiasm are enough.

Rosewall hopes this success will encourage more scientists to try projects that combine AI and citizen science. She said it was clear that participating in the study enhanced people's enjoyment of the total solar eclipse. Many participants contacted her afterward to share their excitement and emotion.

For team members, it is also one of the most fulfilling projects of their careers. Aguilar said it's the job she's most proud of.

Ordinary people who held up their phones and watched the birds on the day of the total solar eclipse now have their names printed in Science magazine. They not only witnessed an astronomical spectacle, but also participated in the process of revealing the laws of nature.

For those brief four minutes, the moon obscured the sun, and darkness came and went. And long after that, we gained another layer of depth in our understanding of how life perceives the world.

References

[1]Liz A. Aguilar et al, The importance of light for bird behavior, as revealed by community science and the 2024 eclipse, Science (2025). DOI: 10.1126/science.adx3025. www.science.org/doi/10.1126/science.adx3025