The sound of magpies warbling in the morning is synonymous with life in Australia, but Perth researchers are predicting a bleak future for the beloved species.
- Heat stress affects a magpie’s cognition and ability to feed and care for chicks
- Magpie chicks often die in heatwaves with survival rates as low as 10 per cent
- Birds find it hard to recover from weight loss during heatwaves
Research conducted by associate professor Amanda Ridley and her team at the University of Western Australia has found that very hot weather is affecting the birds’ ability to survive, reproduce and raise their chicks.
Dr Ridley, who has been collecting data on magpies since 2013, said heatwaves had devastated the birds and their babies over the past three summers.
“During that very bad heatwave (in 2019-2020), which caused terrible bushfires all across Australia, we had zero reproductive success,” Dr Ridley said.
“All the babies that were alive during that heatwave died before it ended.
The Western Australian Climate Projections summary, a document prepared by the state government, predicts the number of very hot days over 35 degrees Celsius in WA’s South West will increase from 28 to 36 by 2030, under an “intermediate emissions scenario”.
By 2090, the number of days would increase to 63.
Dr Ridley and her team, the Western Magpie Research Project, work with multiple groups of wild but tame birds across Perth.
She said the more recent heatwave over the 2021 holiday period had also affected the birds.
The team’s research has found that the magpies suffer cognitive decline when the temperature reaches around 32 to 33 C.
They experience heat stress which hinders their ability to forage for food and feed their babies.
“What we also found is that they were trading off investment in the babies,” Dr Ridley said.
“So, when it came to having to make sure they were gaining enough body mass, they would abandon their babies.
“The babies weren’t being fed on those really hot days, and that’s causing the babies to die.”
With chicks facing more barriers to survival, Dr Ridley said there were issues with fewer juvenile birds reaching breeding age, and those that did often had stunted development which affected their success as adults.
Number of birds might be deceiving
“At the moment, people see magpies around a lot; they think magpies are really common, but the thing with magpies is that they’re long-lived,” Dr Ridley said.
“So, these adults that you’re seeing around … can live for 20 years.
“But what’s important is that juveniles come through and are recruited to breeding adults. And we’ve seen recently that that’s not happening.”
Recruitment, she said, was when juveniles joined the social group as breeding adults, maintaining the group’s size by replacing other adults when they die.
Dr Ridley is yet to collate her data into projections to estimate the exact risk and timeline of population decline in magpies.
African birds present troubling picture
However, she has compiled projections using data on another bird called a pied babbler, which has a similar body mass and lives in a part of South Africa with a similar climate to Perth.
She said more than 30 per cent of predictions said that the babbler population would become extinct in hot and dry conditions.
“That was quite a wake-up call for us, because you see them everywhere you think they’re going to be fine,” Dr Ridley said.
“But every species is affected by climate change, and they’re potentially facing a cliff – that breakpoint of their tolerance – that they’re going to fall off.”
Dr Ridley said other groups doing similar research were also seeing “breakpoints” once it got too hot.
“I think it is probably quite a solid representation of what’s happening to a lot of bird species,” she said.
Dr Ridley added that providing water for the magpies in hot weather is one way to help the birds.