Research to support birds’ survival
DURING the northern hemisphere summer of 2022, yet another round of extreme heat waves roasted Eurasia, North America and northern Africa – a stark reminder that these conditions are becoming the new normal.
These events can have a devastating impact on wildlife. For instance, reports of large-scale deaths of birds have become regular in recent years in Patagonia, Argentina and Spain.
These events underscore the need to understand the ability of birds (and other animals) to tolerate extreme heat. This information will be essential for predicting where and when future mortality events could occur. It can also tell us which species will be most affected.
Intriguingly, when we conducted a study to measure how much heat 53 bird species in southern Africa could stand, we found species vary greatly in the way they handle heat.
Most significantly, how hot a bird’s body temperature could get – what we call “maximum tolerable body temperature” – differed in unexpected ways among bird species from different climatic regions. This suggests birds from different climates will handle extreme heat differently.
This is an important finding. Previous research assumed the body temperature response to extreme air temperatures for birds was similar between species. Predictions on how vulnerable birds are to climate change have been modelled with this thinking in mind.
Our study shows the reality is more complex. Birds may have evolved depending on where they lived, to have variation in traits like body temperature and ability to handle heat.
Assuming that birds all handle heat in the same way could result in predictions that don’t reflect how vulnerable they truly are to global warming.
To improve the accuracy of such predictions, the body temperature limits of specific species need to be incorporated. Our study examined 53 bird species from hot arid, cool mountainous or warm humid coastal regions of southern Africa.
We found desert birds comfortably handled air temperatures exceeding 50°C, without a dramatic increase in body temperature. They maintained body temperatures below about 44.5°C.
Birds from warmer, humid regions tolerated air temperatures in the upper 40s before showing signs of severe hyperthermia. Their body temperatures increased on average almost 6°C above normal levels of 38-41°C.
Generally, large fluctuations in a bird’s body temperature during heat exposure suggests the bird isn’t able to maintain optimal body temperatures.
The findings of our study are highly relevant for understanding the risks posed by extreme heat waves. For instance, our findings confirm previous suspicions that songbirds – over half of all bird species on Earth – are particularly vulnerable to heat waves.
Developing strategies to mitigate the effects of these events on birds and other wildlife is crucial, as extreme heat events are becoming more regular and widespread.
They pose increasing risks to the region’s remarkable biodiversity.
Management interventions in protected areas may reduce the likelihood of future mortality events. Maintaining shady vegetation, for instance, provides cool places where birds can escape.