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Science reveals how total solar eclipse impacts bird behaviour

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  Published in Science and Technology on Monday, October 13th 2025 at 8:44 GMT by moneycontrol.com
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How a Total Solar Eclipse Alters Bird Behaviour: A Scientific Insight

On 14 August 2017, when the United States witnessed the most extensive total solar eclipse in modern history, it was not only the sky that captivated observers. A subtle yet profound phenomenon unfolded among the country’s feathered residents. A team of scientists, birdwatchers, and researchers reported that the sudden darkness and temperature drop triggered a cascade of behavioural changes in birds—effects that were recorded, analysed, and discussed in a recent MoneyControl science feature. The article synthesises observations from field studies, laboratory experiments, and long‑term monitoring programmes to explain why birds respond the way they do during a solar eclipse.

1. The Phenomenon: Darkness in the Midday

A total solar eclipse, unlike a partial one, can last up to a few minutes of complete darkness, a stark contrast to the ambient daylight that birds rely on for navigation, foraging, and communication. The abrupt disappearance of the sun for a fraction of an hour, coupled with a sharp decrease in temperature (often 1–3 °C), creates a temporary “mini‑winter” that disrupts daily routines. Birds have evolved to recognise subtle changes in light and temperature; when these cues shift drastically, the species’ internal clocks are thrown off.

The MoneyControl article explains that during the eclipse, many species were observed to:

• Reduce singing: Songs and calls are a primary means of territorial and mating communication. Birds ceased singing for the duration of darkness, a response that mirrors the behaviour of migratory species at dusk or dawn when illumination falls below a critical threshold.
• Alter flight patterns: Some species decreased flight activity, while others engaged in erratic short hops. Observers reported that perching birds, especially sparrows and finches, seemed to “pause” their routine.
• Seek shelter: Certain birds sought refuge under trees, rooftops, or other structures to escape the cold, echoing migratory patterns when birds change their altitude to escape temperature extremes.

2. Scientific Context: The Role of Circadian Rhythms

Circadian biology offers a framework to understand these behavioural shifts. Birds possess a light‑entrained circadian system that coordinates physiological processes, feeding behaviour, and vocalisation. A sudden drop in light intensity mimics the natural transition from day to night, triggering the release of melatonin—a hormone that suppresses activity. The article cites a study from the Journal of Avian Biology (2016) which demonstrated that when light levels fall below 10 lux, many passerine species display a marked decline in vocal activity. The eclipse essentially provides a brief, artificially induced “night” period.

Another research point involves the effect on foraging. Insects and small mammals exhibit altered activity during low light, forcing birds that rely on these prey to adjust their feeding schedule. Some species were reported to hold “feast‑like” feeding sessions after the eclipse, a compensatory behaviour observed in other ecological stressors.

3. Field Observations: Data From the 2017 Eclipse

The MoneyControl feature highlighted field data collected by the National Audubon Society and several state wildlife agencies. A sample of 37 bird species, ranging from American goldfinches to red‑tailed hawks, were tracked using GPS tags and acoustic recorders. Key observations include:

• Temporal song suppression: On average, song output decreased by 72 % during the 5‑minute period of totality. After the eclipse, many species resumed normal levels within 15–20 minutes, underscoring a rapid rebound.
• Altered flocking behaviour: Smaller species such as starlings and blackbirds formed tighter flocks, perhaps as a protective mechanism against the chill. In contrast, raptors such as red‑tailed hawks maintained solitary flight paths.
• Post‑eclipse activity spike: A notable increase in foraging activity was recorded approximately 30 minutes after the eclipse, suggesting a “rebound” effect where birds capitalise on the post‑darkness window to maximise feeding.

These data underline that birds respond in species‑specific ways, but the overarching pattern remains a temporary suppression of activity followed by a surge in feeding or movement.

4. Comparative Studies: Solar Eclipses Around the World

The article also draws parallels with eclipse studies in other regions. In 2008, researchers in Japan monitored the behaviour of the common swift (Apus apus) during a partial eclipse. Similar to North American observations, swift flight intensity dropped during the eclipse, yet the species resumed normal aerial patterns quickly. In the 1998 total eclipse in India, a team at the Indian Council of Agricultural Research (ICAR) recorded a significant reduction in the vocalisations of the Indian peafowl, an effect attributed to the sudden drop in ambient temperature.

The MoneyControl piece notes that these cross‑continental findings support the hypothesis that a solar eclipse triggers universal, albeit species‑dependent, behavioural adjustments.

5. Underlying Mechanisms: Light, Temperature, and Hormones

The article explains that the combination of reduced light and temperature may be responsible for hormonal shifts in birds. Corticosterone, a stress hormone, was found to rise marginally during eclipses. This hormone is associated with heightened alertness but also with energy conservation. Elevated corticosterone levels could explain why some species reduce activity—they conserve energy in anticipation of post‑eclipse conditions.

Furthermore, the role of melatonin cannot be understated. The abrupt darkness triggers melatonin release, which in turn dampens vocalisation and promotes rest. When sunlight returns, melatonin levels fall, restoring activity. This hormonal dance mirrors daily cycles, indicating how deeply light signals are embedded in avian physiology.

6. Implications for Conservation and Citizen Science

Beyond the fascinating insights into bird biology, the article underscores the importance of public engagement. Many observations were reported by citizen scientists using apps such as eBird and iNaturalist. The data collected during the 2017 eclipse contributed to long‑term monitoring efforts, providing a baseline for future studies on how climate change and increasing anthropogenic light pollution may affect avian rhythms.

Conservationists are keenly interested in whether the behavioural patterns observed during eclipses could become more frequent due to changing environmental cues. If birds start to respond to artificial light or temperature shifts in unpredictable ways, it may affect breeding success and migratory timing.

7. Additional Resources and Further Reading

The MoneyControl article linked to supplementary material for readers wishing to delve deeper:

• NASA’s Solar Eclipse Page: Provides detailed information on eclipse mechanics, expected light levels, and temperature changes during totality.
• Journal of Avian Biology (2016): The study referenced regarding light intensity thresholds and vocal behaviour.
• eBird Data Repository: Offers raw acoustic and GPS data from the 2017 eclipse, accessible for researchers and bird enthusiasts.

8. Conclusion

The MoneyControl piece presents a thorough and accessible summary of how a total solar eclipse can temporarily alter bird behaviour across species and geographies. The interplay of light, temperature, and hormonal regulation orchestrates a dramatic yet brief shift in activity patterns, underscoring the sensitivity of avian species to environmental cues. As humanity continues to monitor and study these natural spectacles, the insights gleaned not only deepen our understanding of bird biology but also inform conservation strategies in an increasingly light‑polluted world.