2023-10-09 ミシガン大学
Conceptual and geographic layout of the study system. Space weather from the sun, such as coronal mass ejections, disturb Earth’s magnetic field, causing the auroras and potentially decreasing the magnetic field’s reliability for migrating birds. Image credit: John Megahan, University of Michigan, from Gulson-Castillo et al. in PNAS, October 2023
◆米国ミシガン大学の研究者たちは、米国の気象レーダーステーションと地磁気計のデータを使用して、地磁気の乱れと渡り鳥の移動との関係を調査しました。その結果、宇宙天候イベントの際に春と秋の両方で渡り鳥の数が9%から17%減少し、特に秋の曇りの日に航法が難しくなることが明らかになりました。これにより、地磁気の乱れと夜行性鳥の渡りに新たな関連性が示され、環境条件が動物の移動パターンに影響を与えることが強調されました。
<関連情報>
- https://news.umich.edu/space-weather-disrupts-nocturnal-bird-migration-study-finds/
- https://www.pnas.org/doi/abs/10.1073/pnas.2306317120
宇宙天気は夜行性の鳥の移動を混乱させる Space weather disrupts nocturnal bird migration
Eric R. Gulson-Castillo, Benjamin M. Van Doren https://orcid.org/0000-0002-7355-6005, Michelle X. Bui, Kyle G. Horton, Jing Li, Mark B. Moldwin, Kerby Shedden, Daniel T. Welling, and Benjamin M. Winger
Proceedings of the National Academy of Sciences Published:October 9, 2023
DOI:https://doi.org/10.1073/pnas.2306317120
Significance
Birds and other animals depend on Earth’s magnetic field for long-distance navigation during their seasonal migrations. However, the magnetic field is regularly disrupted by bursts of solar energy, which may temporarily decrease its reliability for navigation. We used long-term datasets derived from Doppler radar and magnetometers to test whether geomagnetic disturbance is correlated with the number of birds migrating, their effort flying against the wind, and their flight altitude. Our results suggest that fewer birds migrate during strong geomagnetic disturbances and that migrating birds may experience more difficulty navigating, especially under overcast conditions in autumn. Our results provide ecological context for decades of research on the mechanisms of animal magnetoreception by demonstrating community-wide impacts of space weather on migration dynamics.
Abstract
Space weather, including solar storms, can impact Earth by disturbing the geomagnetic field. Despite the known dependence of birds and other animals on geomagnetic cues for successful seasonal migrations, the potential effects of space weather on organisms that use Earth’s magnetic field for navigation have received little study. We tested whether space weather geomagnetic disturbances are associated with disruptions to bird migration at a macroecological scale. We leveraged long-term radar data to characterize the nightly migration dynamics of the nocturnally migrating North American avifauna over 22 y. We then used concurrent magnetometer data to develop a local magnetic disturbance index associated with each radar station (ΔBmax), facilitating spatiotemporally explicit analyses of the relationship between migration and geomagnetic disturbance. After controlling for effects of atmospheric weather and spatiotemporal patterns, we found a 9 to 17% decrease in migration intensity in both spring and fall during severe space weather events. During fall migration, we also found evidence for decreases in effort flying against the wind, which may represent a depression of active navigation such that birds drift more with the wind during geomagnetic disturbances. Effort flying against the wind in the fall was most reduced under both overcast conditions and high geomagnetic disturbance, suggesting that a combination of obscured celestial cues and magnetic disturbance may disrupt navigation. Collectively, our results provide evidence for community-wide avifaunal responses to geomagnetic disturbances driven by space weather during nocturnal migration.
