The total solar eclipse on April 8, 2024, was a stunning event, but it had more than just a visual impact. New research shows that it actually reset the biological clocks of various bird species in North America.
When the moon blocked the sun, it turned midday into a brief period of total darkness along a path stretching from Mazatlán, Mexico, to St. John’s, Newfoundland. During this unique moment, scientists observed that 29 bird species burst into song, acting as if dawn had arrived. Researchers shared these findings in the journal Science.
Interestingly, many of these observations came from citizen scientists who contributed valuable data throughout the eclipse’s path. Their involvement allowed researchers to collect a broader range of information. According to Liz Aguilar, a lead author of the study and a doctoral candidate at Indiana University, the eclipse served as a natural experiment. It provided insights into how birds react to sudden changes in light—something that is hard to replicate in a lab. Total solar eclipses happen in the same area just once every few centuries, meaning many wild birds have never experienced one before.
Aguilar noted that light plays a crucial role in shaping bird behavior. A mere four minutes of darkness was enough for these creatures to behave as if morning had come again. “This sensitivity to light has significant implications,” she pointed out, especially concerning issues like light pollution.
A similar study during the 2017 eclipse had shown that some animals in captivity, including birds, altered their behavior under similar conditions. However, Aguilar and her team focused on wild species. Spring was the ideal time for this study, as many birds were busy vocalizing to attract mates and defend their territory.
The researchers created a smartphone app called SolarBird to engage the public and document bird behavior. About 11,000 observations from over 1,700 users were collected during the eclipse, tracking how birds reacted before, during, and after. Tissue recorders were also set up across southern Indiana to capture around 100,000 bird vocalizations.
Experts analyzed the data using BirdNET, an AI system that identifies bird species based on their calls. Among the 52 species active during the eclipse, 29 showed noticeable changes in their vocalizations. For instance, 11 species sang more than usual, while others either fell silent or became more active. The most dramatic response was seen when light returned—19 species erupted into what researchers dubbed a “false dawn chorus.”
Notably, specific birds like barred owls called four times more frequently, and robins sang six times their usual amount. Aguilar explained that the return of sunlight essentially reset their biological clocks.
Different species reacted uniquely. Birds that typically have rich dawn choruses were the most responsive to the eclipse. While the study focused on immediate behavioral changes, Aguilar suggested that longer-term effects were likely minimal. Still, the time spent reacting to the darkness could have been better used for foraging or mating.
Dr. Andrew Farnsworth from the Cornell Lab of Ornithology, who studied bird behavior during both the 2017 and 2024 eclipses, emphasized that these findings shed light on how birds perceive and adapt to their environments.
With the increasing problem of light pollution, understanding which bird species are most affected is crucial. A recent study indicated that light pollution can lead birds to sing longer and can disorient migrating species, increasing fatal collisions with buildings.
Fortunately, there’s a growing effort to combat light pollution, which could help various animal species. Knowing which birds are most impacted can help focus conservation efforts effectively.
For anyone keen to learn more about this topic, further reading can be found in the original study from Science. Understanding the behaviors and reactions of these birds not only fascinates us but also highlights the importance of preserving their natural environments amidst our changing world.
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