Tropical bird populations are crashing as temperatures soar. That’s according to a new study that found abundances of tropical birds were 25-38% lower than they would be without human-driven climate change and the rising temperatures it has caused.
This temperature impact on birds is greater than declines attributed to deforestation.
“It’s a staggering decrease. Birds are particularly sensitive to dehydration and heat stress,” lead author Maximilian Kotz, a researcher at the Barcelona Supercomputing Center, said in a statement. “Extreme heat drives excess mortality, reduced fertility, changing breeding behaviors and reduced offspring survival.”
The authors fed decades of bird data into computational models to estimate the impact climate change has had on tropical bird populations, particularly where monitoring is insufficient.
The researchers argue that extreme heat may help explain mysterious bird population declines even in intact rainforests that haven’t been subjected to logging or hunting.
“Rising temperatures are really pushing species out of the ranges that they’ve naturally adapted to — and in a very short amount of time,” Kotz said. “Ultimately, our emissions are at the heart of this issue.”
Songbirds, which make up more than 60% of all bird species, were found to be the most sensitive to changes in extreme temperatures, though the researchers warn that their study shouldn’t be used to analyze specific species. Other studies have recorded similarly dramatic declines. In the Ecuadorian Amazon, earlier research documented a 50% decline in several bird species over 22 years in an area of forest without any documented deforestation, pesticide use or hunting.
“There’s something called the dawn chorus, which is typical in tropical forests where lots of birds sing just before dawn,” John Blake, one of the researchers in Ecuador, told Mongabay. “Over the last 10 years, that has just been going quieter and quieter with very few birds singing.”
In a conserved Panamanian forest, the tropical royal flycatcher (Onychorhynchus coronatus) population declined by more than 95% from 1977 to 2022. The Amazonian black-throated trogon (Trogon rufus) and the red-capped manakin (Ceratopipra mentalis) declined by more than 60% in the same period.
Forty years ago, the tropics experienced an average of three days a year of extreme heat. Today, the number has increased tenfold to 30 days.
“We are so used to thinking about average temperature and overall human impacts (urbanization, pollution, etc.) that it is easy to forget how consequential a few days of extreme conditions can be for wild animals,” Conor Taff, a researcher at the Cornell Lab of Ornithology in the U.S., who wasn’t involved in the study, told Mongabay by email.
“Unfortunately, it seems likely that exposure to extreme temperatures is going to continue increasing and it isn’t as easy to tackle from a conservation priority perspective as land use and wildlife management policy might be,” Taff added.
Banner image: The tropical royal flycatcher has suffered a decline in abundance. Image by Crístian Rincón Alvarez via iNaturalist (CC BY-NC 4.0).
