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An international research team formed by Associate Research Fellow Mao-Ning Tuanmu at the Biodiversity Research Center, Academia Sinica, together with collaborators from the United Kingdom and the United States, has confirmed that the unusual phenomenon of some montane birds moving to higher elevations in winter is linked to interspecific competition, based on the integration of theoretical models and large-scale citizen science observation.

Using more than 20 years of data from the citizen science platform eBird, the researchers analyzed nearly 11,000 bird populations across 34 mountain regions worldwide. They found that about one-third of montane birds undertake elevational migration, moving hundreds of meters up and down annually. This pattern occurs not only in temperate regions but also in tropical mountains where seasonal temperature variation is minimal. Notably, many species move upslope in winter rather than downslope to warmer areas. This counterintuitive pattern suggests that birds do not migrate solely to track favorable climates; instead, they balance food availability, energetic costs, and competition to select the most advantageous habitats.

The findings validate a hypothesis proposed by Dr. Tuanmu’s team in 2021 and challenge the long-standing view that climate is the primary driver of migration. Instead, the study highlights the key roles of ecological interactions and energy allocation in shaping species distributions. The results also improve our ability to predict how montane birds and biodiversity may respond to climate change and human disturbance, providing valuable insights for conservation strategies and policy development.

This study was supported by a bilateral research grant from Taiwan’s National Science and Technology Council and the Royal Society of the United Kingdom, awarded to Dr. Mao-Ning Tuanmu and Dr. Marius Somveille from the University of East Anglia. The findings were published in Science Advances in February 2026.