Birds evolve different body temperatures in different climates—new study of 53 African species
Red-billed quelea adult breeding male. Credit: Linn Currie/Shutterstock

It was a stark reminder that these conditions are becoming the new normal during the summer of 2022.

There can be a huge impact on wildlife. Large-scale deaths of birds have become a regular occurrence in recent years.

Birds and other animals are able to tolerate extreme heat. Predicting where and when mortality events will occur is dependent on this information. Which species will be most affected is possible.

When we measured how much heat 53 bird species in southern Africa could tolerate, we found that they varied greatly in how they handled heat.

In unexpected ways, how hot a bird's body temperature could get differed from region to region. Birds from different climates are likely to handle heat differently.

This is significant. It was assumed that the body temperature response for birds was the same as for other animals. Predicting the vulnerability of birds to climate change has been done.

The reality is more complicated. Birds may have evolved based on where they lived, to have different body temperature and heat tolerance.

It could result in predictions that don't reflect how vulnerable birds really are to global warming. Body temperature limits of specific species are needed to improve the accuracy of predictions.

The body temperature is regulated in the heat.

We looked at 53 bird species from hot arid, cool mountainous or warm humid coastal regions of southern Africa.

Birds from different parts of the world differed in their body temperatures. At increasing air temperatures, we measured the birds' body temperature, metabolism and water loss. Bird pants allow it to cool down, which leads to water loss.

The maximum body temperature was something we were interested in. We were able to measure this before birds showed signs of loss of co-ordination and increases in body temperature. Both of those symptoms are related to the start of overheating.

Desert birds did not experience a dramatic increase in their body temperature when temperatures exceeded 50C. The body temperature was approximately 44.5C.

The birds from warmer, humid regions did not show signs of severe hyperthermia until they reached the upper 40s. Their body temperatures went up by six degrees.

Large fluctuations in a bird's body temperature suggest that the bird isn't able to maintain optimum body temperatures.

One species, the red-billed Querlea, can cope with a body temperature increase of 48C without any ill effects. It was thought to be impossible for birds.

The evolution of heat tolerance.

Why did birds become tolerant of high temperatures?

Birds from more humid areas have adapted to cooler weather.

vaporative cooling is when a bird loses heat by panting It's the only way a bird can get rid of heat when its temperature is higher than its body temperature. A bird can survive in a humid area if it can tolerate a high body temperature.

Birds which have evolved in humid climates are able to tolerate the heat. Desert birds use cool air to avoid heat.

The evolution of body temperature and heat tolerance among birds from different climates is suggested by this.

Birds are protected from heat.

Understanding the risks posed by extreme heat waves to birds and other wildlife is related to the findings of our study. Our findings show that songbirds, which make up over half of all bird species on Earth, are particularly vulnerable to heat waves.

Extreme heat events are becoming more frequent and widespread across southern Africa, so developing strategies to mitigate the effects is important. They pose a risk to the region's unique flora and fauna.

On November 8, 2020, the air temperature in the Pongola area soared to 45C, showing the risks that were present. There were a lot of birds that died due to this. The birds that were found dead in the Phongolo Nature Reserve were mostly songbirds.

There are management interventions in protected areas. Birds can escape the worst of the heat if the vegetation is maintained well. Water sources that are free-standing will increase the likelihood that birds can defend themselves.

Rapid decarbonisation of economies and a global transition to renewable energy sources are the only ways to prevent large-scale losses of bird biodiversity.

There is more information about the adaptive variation in the upper limits of the bird's body temperature. 10.1073/pnas.

Journal information: Proceedings of the National Academy of Sciences

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