The numbers of many tropical birds are plummeting, and now it has been shown that heat extremes intensified by global warming are the biggest factor driving these declines
By Michael Le Page
11 August 2025
The Amazonian black-throated trogon is in sharp decline
LuismiX/Getty Images
In tropical regions such as the Amazon and Panama, the populations of some birds have fallen by as much as 90 per cent even in mostly untouched rainforests. Now, research has found that more intense heat extremes are likely to be the main factor behind these declines.
Between 1950 and 2020, the intensification of heat extremes led to a fall of between 25 and 38 per cent in the abundance of land-dwelling birds in the tropics, according to a new study by Maximilian Kotz at the Barcelona Supercomputing Center and his colleagues.
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The team hasn’t yet used these results to try to project what will happen as the planet continues to heat up, but the outlook is clearly alarming. “It’s not a good-looking picture,” says Kotz.
He and colleagues started with data on land-dwelling bird populations around the world from the Living Planet Database. The study didn’t include water birds or seabirds. They then got data on habitat destruction from the Hyde Database of the Global Environment and historical weather and climate data from the European Centre for Medium-range Weather Forecasts.
The researchers compared all this data to find correlations that might explain the observed changes in bird abundance. In the mid-latitudes between 21° and 43° north or south, habitat destruction was the main factor driving declines, their findings suggest, in line with other studies.