The birds' wings have been clipped by the lethal heat. Research findings indicate that heatwaves and droughts induced by global warming have significantly reduced the population of tropical birds.
An international research team, including the Max Planck Institute for Meteorology in Germany and the Barcelona Supercomputing Center in Spain, published these research results in the international journal "Nature Ecology & Evolution" on the 12th.
Tropical regions are a treasure trove of biodiversity, hosting half of the world's bird species. However, their populations have greatly declined due to overexploitation, habitat destruction, and the introduction of invasive species since the Industrial Revolution. Recently, temperature changes have also emerged as a risk factor for birds.
To quantify the impact of climate change on tropical birds, the research team analyzed over 90,000 data points from observations of more than 3,000 bird populations worldwide between 1950 and 2020. They isolated the effects of extreme heat, excluding influences from temperature and precipitation changes as well as human activities. Extreme heat refers to days with temperatures in the top 1% of historical records.
The analysis revealed that since 1950, the global population of tropical birds has decreased by an average of 25-38% due to heatwaves linked to climate change. The decline in tropical birds has been observed even in areas without human development or habitat destruction.
In particular, the number of "heatwave days" was found to be much more strongly associated with the decline in bird populations than average temperature increases or changes in precipitation. In tropical regions, the cumulative effects of these heatwaves were greater than direct human interference. These impacts were consistently observed regardless of bird classification, migratory habits, or analytical methods.
The research team noted, "It has been confirmed that the main cause of the decline in tropical bird populations is heatwaves due to climate change," adding, "If greenhouse gas emissions are not reduced, the intensity and frequency of heatwaves will worsen, further diminishing the survival chances of tropical birds."
Earlier, in January, researchers from the Michigan Technological University also released findings indicating that the heat and drought brought on by climate change are threatening bird survival in the Amazon, which is a representative tropical rainforest.
Previously, it was believed that the deep, pristine forests of the Amazon were safeguarded from climate change. This belief stemmed from the idea that dense forests block light and heat, stabilizing the temperature within the forest. However, actual observations yielded different results.
Research conducted by the team in the Brazilian Amazon over 27 years, observing 4,264 tropical birds, found that when the dry season is hotter and has less rainfall than usual, the survival rates of 24 out of 29 species significantly decline. When the average temperature during the dry season rises by just 1 degree Celsius, the average survival rate of Amazonian birds drops by an astonishing 63%.
The research team from Michigan Technological University stated, "The increasingly severe heat and drought of the dry season pose a direct threat to bird survival," emphasizing that "merely protecting the forest is insufficient; strategies for mitigating and adapting to climate change must be developed together."
References
Nature Ecology & Evolution (2025), DOI: https://doi.org/10.1038/s41559-025-02811-7
Science Advances (2025), DOI: https://doi.org/10.1126/sciadv.adq8086