Tuesday, 14 October, 2025
A total solar eclipse swept across North America on April 8, 2024, tracing a 2,500-mile (4,000-km) path from Mexico’s Pacific coast through Texas and across 14 U.S. states into Canada. The period of totality—when the moon completely obscured the sun—lasted up to four minutes, depending on the location.
While millions of skywatchers marveled at the rare celestial spectacle, scientists focused on how the sudden darkness affected bird behavior. Since many bird species rely heavily on light cues to regulate their daily and seasonal activities, researchers observed noticeable shifts in their vocal patterns.
The study found that most—but not all—bird species altered their calls during the eclipse. Birds known for their energetic “dawn chorus” at daybreak were the most affected. As sunlight reappeared after totality, some species began singing as if a new morning had arrived, mistaking the returning light for sunrise. Others, however, remained silent or behaved much as they would on an ordinary day.
"Light is one of the most powerful forces shaping bird behavior, and even a four-minute 'night' was enough for many species to act as if it were morning again. That tells us just how sensitive some birds are to changes in light," said Liz Aguilar, a doctoral student in evolution, ecology and behavior at Indiana University and lead author of the study published this week in the journal Science.
"Based on previous research, most of which was collected in the lab, we know that changes in light are the most important cues used by living organisms to time their daily rhythms. As day transitions to night and vice versa, hormone levels and gene expression in the body change, and that causes differences in behavior," said study co-author Dustin Reichard, a biology professor at Ohio Wesleyan University.
While there had been anecdotal evidence concerning the behavior of birds during an eclipse and some research involving certain species, this study offered the most comprehensive look yet at the subject, with the findings coming from two datasets.
Fourteen recording units placed around Bloomington, Indiana, captured more than 100,000 bird vocalisations that were analysed using machine-learning tools to discern the individual species making the songs and calls. In addition, nearly 1,700 people across North America submitted more than 11,000 observations of bird behavior around the eclipse through an app created by the researchers called SolarBird that let anyone in the general public with a smartphone contribute data.
A total of 52 species were documented around Bloomington, 29 of which exhibited significant changes in their vocal behavior as the eclipse occurred compared to a normal April afternoon.
"Different bird species greet the dawn in very different ways. Some have loud, elaborate dawn choruses, while others are much quieter. We found that species known for the most intense dawn choruses were also the ones most likely to react to the eclipse," Aguilar said.
Different bird species reacted to the eclipse in markedly different ways. American robins, famous for singing in the early morning darkness before sunrise, showed one of the most dramatic responses — their vocal activity increased sixfold during and immediately after totality compared with a normal afternoon.
Barred owls also grew more vocal, calling four times more often than usual once the eclipse ended, when light levels briefly mimicked the dim conditions of dawn or dusk — periods when their activity typically peaks.
In contrast, Carolina wrens, another species known for their persistent and energetic songs, appeared entirely unaffected by the temporary darkness.
“It actually makes sense that not all species reacted the same way,” said Aguilar, the study’s lead author. “Birds differ in how sensitive they are to changes in light. It would have been more surprising if every species responded identically. Each has its own activity patterns, energy needs, and sensory abilities — so they interpret environmental changes differently.”
Aguilar added that the researchers looked for behavioral patterns among closely related species and compared migratory and resident birds, but found no consistent differences. “That tells us there’s still more to learn about what makes certain species more or less sensitive to sudden changes in light — an important direction for future research,” she said.
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A total solar eclipse swept across North America on April 8, 2024, tracing a 2,500-mile (4,000-km) path from Mexico’s Pacific coast through Texas and across 14 U.S. states into Canada. The period of totality—when the moon completely obscured the sun—lasted up to four minutes, depending on the location.
While millions of skywatchers marveled at the rare celestial spectacle, scientists focused on how the sudden darkness affected bird behavior. Since many bird species rely heavily on light cues to regulate their daily and seasonal activities, researchers observed noticeable shifts in their vocal patterns.
The study found that most—but not all—bird species altered their calls during the eclipse. Birds known for their energetic “dawn chorus” at daybreak were the most affected. As sunlight reappeared after totality, some species began singing as if a new morning had arrived, mistaking the returning light for sunrise. Others, however, remained silent or behaved much as they would on an ordinary day.
"Light is one of the most powerful forces shaping bird behavior, and even a four-minute 'night' was enough for many species to act as if it were morning again. That tells us just how sensitive some birds are to changes in light," said Liz Aguilar, a doctoral student in evolution, ecology and behavior at Indiana University and lead author of the study published this week in the journal Science.
"Based on previous research, most of which was collected in the lab, we know that changes in light are the most important cues used by living organisms to time their daily rhythms. As day transitions to night and vice versa, hormone levels and gene expression in the body change, and that causes differences in behavior," said study co-author Dustin Reichard, a biology professor at Ohio Wesleyan University.
While there had been anecdotal evidence concerning the behavior of birds during an eclipse and some research involving certain species, this study offered the most comprehensive look yet at the subject, with the findings coming from two datasets.
Fourteen recording units placed around Bloomington, Indiana, captured more than 100,000 bird vocalisations that were analysed using machine-learning tools to discern the individual species making the songs and calls. In addition, nearly 1,700 people across North America submitted more than 11,000 observations of bird behavior around the eclipse through an app created by the researchers called SolarBird that let anyone in the general public with a smartphone contribute data.
A total of 52 species were documented around Bloomington, 29 of which exhibited significant changes in their vocal behavior as the eclipse occurred compared to a normal April afternoon.
"Different bird species greet the dawn in very different ways. Some have loud, elaborate dawn choruses, while others are much quieter. We found that species known for the most intense dawn choruses were also the ones most likely to react to the eclipse," Aguilar said.
Different bird species reacted to the eclipse in markedly different ways. American robins, famous for singing in the early morning darkness before sunrise, showed one of the most dramatic responses — their vocal activity increased sixfold during and immediately after totality compared with a normal afternoon.
Barred owls also grew more vocal, calling four times more often than usual once the eclipse ended, when light levels briefly mimicked the dim conditions of dawn or dusk — periods when their activity typically peaks.
In contrast, Carolina wrens, another species known for their persistent and energetic songs, appeared entirely unaffected by the temporary darkness.
“It actually makes sense that not all species reacted the same way,” said Aguilar, the study’s lead author. “Birds differ in how sensitive they are to changes in light. It would have been more surprising if every species responded identically. Each has its own activity patterns, energy needs, and sensory abilities — so they interpret environmental changes differently.”
Aguilar added that the researchers looked for behavioral patterns among closely related species and compared migratory and resident birds, but found no consistent differences. “That tells us there’s still more to learn about what makes certain species more or less sensitive to sudden changes in light — an important direction for future research,” she said.
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