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Golden bowerbirds' building prowess helps scientists monitor climate change, and alarm bells are ringing

Emma Siossian, Saturday June 8, 2019 - 18:52 EST
Audience submitted image
The golden bowerbird builds a huge bower, which it decorates with lichen, flowers and seedpods. - Audience submitted

They chirp, whistle, buzz, bob and dance, and male bowerbirds are among the best architects and decorators in the bird world.

They build intricately constructed, brightly decorated bowers, which become the stage for a ritualised performance of dancing and singing, all designed to attract a female.

Dr Clifford Frith, Australian ornithologist and bowerbird expert, said the fascinating behaviour was part of a powerful evolutionary process of sexual selection.

"The males of the species build bowers that are architecturally so complex and beautiful," he said.

"The early explorers to New Guinea and Australia refused to believe when they were told by the native people that they [the bowers] were made by birds — they assumed they were made by parents to entertain their children," he said.

The smallest of the 10 species of bowerbirds in Australia, the golden bowerbird, builds the largest bowers.

The towering maypole-type structures can rise to three metres and are constructed around two trees.

The giant bowers are then maintained in the same place for decades.

"Our studies show that some golden bowerbird bowers will persist for up to 40 years in the same spot. Generation after generation take over the bowers," Dr Frith said.

"It does mean of course that each male at his bower is constantly under pressure from younger males seeking to establish themselves; they are literally waiting for dead man's shoes."

Indicators of climate change

The golden bowerbird's bowers are helping researchers monitor the species as part of climate change studies.

Professor Stephen Williams, from the College of Science and Engineering at Townsville's James Cook University, said the golden bowerbird lived in the highland rainforests of north-east Queensland.

For many years, he has been monitoring the bowerbirds, as well as other Australian highland rainforest species that are restricted to small, high-altitude areas.

"They've adapted to wet, tropical mountain tops. As the temperature increases it pushes them up the mountain and they really have nowhere to go," he said.

"The golden bowerbird is a classic example of that. It typically only occurs on mountain tops above 900 metres of elevation. The mountains are not very high here, so it has really got nowhere to go.

"With the monitoring of the bowerbirds, because they use the bowers and during the breeding season they are very obvious and easy to survey, you can find them and see if they are using those same bowers from one year to the next."

'Alarming and depressing': Climate change happening now

In 2005, a was told that even a 1-degree-Celsius temperature rise would put birds like the Australian golden bowerbird under pressure.

Professor Williams said climate change predictions made more than a decade ago were now becoming a reality.

"We now have quite solid data, based on 15 years of data, that some of these species are contracting quite severely and very much in line with what we were predicting about 10 years ago based on the models, and it's actually happening now," he said.

"It's incredibly alarming and depressing 10 years later to see it actually happening — you hope you're wrong.

"I go out in the field to places I've been to in the last 15 years where I used to see 50 animals in an hour and I go there now and see six or seven."

Professor Williams said there were clear signs both the golden bowerbird, and the tooth-billed bowerbird that also lives in the mountain forests of north-east Queensland, were being affected by warmer temperatures.

"What we have noticed with the tooth-billed bowerbirds, is that they have been consistently disappearing from the lower, hotter parts of the mountain and essentially the population is being shifted up the mountain," he said.

"We see the same sort of thing happening with the golden bowerbirds. We have less data on them, but we see the same pattern happening.

"We've also noticed very severe declines in the lemuroid ringtail possums over the last few years as well.

"It's particularly noticeable when we have the intense summer heatwaves like we did last summer.

"It's the extreme events, the hottest weeks, the droughts, that do the damage."

Watching and being watched

Professor Williams said more monitoring was needed to ensure resources were directed effectively.

"We need to do adaptation research and look at what we can do to stop these species going extinct and stop the environment completely collapsing," he said.

Dr Frith agreed more data was required.

"People need to continue the long-term studies of the bowerbird populations, and that's happening," he said.

"Members of Birdlife Australia are now intensively surveying the presence of the bowers of golden bowerbirds and other bowerbirds in the wet tropics."

Local birdwatchers also monitor bowers, which can offer some golden moments.

Birdwatcher Jennifer Dickinson was patiently waiting at a known golden bowerbird site recently when she realised she wasn't the only one doing the watching.

"We were about to pick up our camera bags and go when we did one last look behind us, and surprise, surprise — there he was, sitting quietly in a tree, just watching us, watching his bower," she said.


© ABC 2019

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