Learning from temperature-sensitive bird species

Ethiopia’s White-tailed Swallow and Bush-crow bird species are unique vulnerability to rising temperatures around their entire, restricted ranges, scientists have discovered. This “climate envelope” could help predict climatic impacts on other species.

The endangered birds are both “star attractions in a region home to five endemic birds,” and “have the potential to become flagship species for the impacts of climate change on avian diversity in Africa,” the researchers write in the journal PLOS ONE.

Two birsd. They are grey with black tails
Ethiopian Bush-crow (Zavattariornis stresemanni), Ethiopia. Credit: Andrew Bladon.

Although the two species have very different origins, ecologies and physical characteristics, the study found they both stay within similar habitats that are cool and dry.

“To find that two species are both limited by temperature at every edge of their global distribution is really quite remarkable,” says lead author Andrew Bladon from the UK’s University of Cambridge.

“These completely unrelated species are influenced very similarly by aspects of the local climate. As the temperature rises due to climate change, they will struggle to survive.”

This is unique as other bird species extensively studied in Europe and North America tend to shift their ranges in response to temperatures in the north and south. The scientists think the two Ethiopian natives could be the only warm-blooded animals whose distribution is determined purely by climate.

The Ethiopian Bush-crow (Zavattariornis stresemanni) has a 4000 square kilometre range, and the perimeter of the area is defined by higher temperatures. It appears the birds are unable to forage for food at temperatures above their limit, as can be seen by their need to pant and find shade.

The White-tailed Swallow (Hirundo megaensis), first recorded in 1942, is found across about 8000 square kilometres of grassland and has never been seen anywhere else, despite extensive searching in similar habitats. Until now this has baffled scientists. With their new insights, the team says it could result from lower breeding success at higher temperatures.

Why these different birds have such similarly defined climatic ranges, characterised by habitats with a mixture of savannah scrub and open grassland interspersed with trees, is unclear.

To derive their findings, the scientists modelled the impacts of several possible future climate change projections from the Intergovernmental Panel on Climate Change (IPCC).

In all case scenarios, they found that both species are at high risk of extinction over the next 50 years as the climate becomes unsuitable for their survival in 68% of the swallow’s and 90% of the crow’s potential range.

Specialist and range-restricted species are some of the most likely to be at risk of extinction, so the team says their modelling approach offers a test case to validate climate models used to inform conservation efforts.

For the White-tailed Swallow and Ethiopian Bush-crow, new understanding of their ranges could help conservationists implement measures such as assisted migration and captive breeding in Ethiopia’s recently created Yabello National Park.

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