/ 9 September 2021

Climate crisis a threat to bird species

Blue Crane (anthropoides Paradisea), Overberg, South Africa, December 2018
Elegant: Blue cranes return to the Overberg each year but climate change may affect their ability to breed. Photo: Marco Valentini/Biosphoto/AFP

It’s South Africa’s national bird and its long feathers are worn by Zulu kings as a sign of royalty. Now the striking blue crane, which numbers about 25 000, has another threat adding to its decline from habitat loss, poisoning and powerline collisions: climate change

“Blue cranes are very dependent on agriculture in the Western Cape, so if climate change leads to major changes to the agricultural system, this could have knock-on effects on cranes,” says Christie Craig, a crane conservationist at the Endangered Wildlife Trust.

Climate predictions foresee the region will become hotter and drier. “It isn’t clear yet how this may change agriculture,” she says. “Some farmers are telling us they will diversify [with crops, livestock and other ventures], which may be good for cranes as they use livestock pastures. However, some farmers say that without rain, pastures don’t grow well, and feeding all year is expensive so they prefer to have croplands only.”

This may mean less habitat for cranes in the winter, when they rely heavily on pasture lands, and also fewer water troughs for the birds. 

“Another concern with hotter temperatures is that cranes breed on the ground during summer and this may mean more nest failures and heat stress for parents incubating.”

The distinctive Cape rockjumper, which is endemic to mountain fynbos, is the first local species to gain a threatened conservation status — near threatened according to the International Union for Conservation of Nature’s Red List — because of the direct and indirect effects of climate change.

BirdLife South Africa chose this species as its bird of the year because it serves as an ambassador for other animal species that are similarly restricted to where they occur because of the “climate envelope” — species that occur in a specific climate niche. 

“While some birds can ‘track’ climate change by moving to where temperature suits them better, this cannot be done for species restricted to the highest altitudes as they can’t move further up,” it says.

Fynbos is protected in CapeNature reserves but there are major concerns about the spread of alien tree species and increased fire frequencies driven by climate change.

“They have a physiology that relies on water-loss to keep cool, an odd strategy given the bird lives in a region that experiences dry summers,” BirdLife South Africa said. Juveniles and chicks seem particularly vulnerable to heat stress, while adults simply stop foraging when it gets too warm. The species, too, is restricted to cooler regions of the fynbos, at higher altitude. 

In a surprising twist, there is evidence that their nests, made on the ground, are becoming vulnerable to predators such as boomslang.

“The predation rates are really high with up to 80% of their chicks being lost,” says Alan Lee, the science and innovation programme manager at BirdLife South Africa. “The warmer temperatures seem to be favouring the arch enemies of the Cape rockjumpers, which may well be more active when it’s warmer.”

The Cape rockjumper’s population numbers about 45 000 individuals. “At the nest predation rates we’re seeing, if those are maintained at 80%, then the extinction horizon is 40 years off, so there is lots of time to make a plan for these guys.”