Why global warming is such a turn-off for Canberra's favourite bird

The reprehensible habits of the superb fairy-wren.

The superb fairy-wren has a magnificent name and bizarre sexual habits. It is not a good model for moral humans who want to do the right thing.

The female mates with two males, tricking the second one into thinking he's the father.

One of her mates is her reliable but dreary partner and the other is a gaudy show-off in bright blue plumage.

This dandy sometimes woos the female by displaying a flower in his beak - if flowers don't always get human females going, they seem to work for the superb fairy-wren.

In this particular disreputable corner of the avian world, the boring brown male seems as though he is aware that his partner is off with another, showier male.

But he still gets it on with her when she returns. This is the "hopeless optimism hypothesis", according to the Australian National University's Andrew Cockburn.

The dreary male mates after the showy one has, in the half hope that he may father offspring - "and that's better than complete failure", Professor Cockburn said.

This is not a good morality tale for humans - but it does illuminate how climate change is disrupting the natural world.

Superb fairy-wren populations in Canberra are declining. Picture: Simon Bennett

Superb fairy-wren populations in Canberra are declining. Picture: Simon Bennett

The superb fairy-wren is one of the Canberra's most popular birds. It is a favourite of gardens across the ACT.

But its population has been savagely cut, according to Professor Cockburn.

He estimates that the sample he studies in the National Botanic Garden is down by about two-thirds, and he cites "this year of pestilence" as partly to blame.

"Apocalyptic catastrophe" is another phrase he uses to describe the effects of climate change.

Researcher Claire Taylor (left) and manager, Helen Osmond, seek out the birds to shoo them towards the net. Picture: Steve Evans

Researcher Claire Taylor (left) and manager, Helen Osmond, seek out the birds to shoo them towards the net. Picture: Steve Evans

With the superb fairy-wren, changing seasons have disrupted breeding habits.

Females want to mate mainly with bright blue, showy males - but the males' plumage only turns a gaudy blue in the right conditions, and global warming is making those conditions less congenial for avian amour.

Professor Cockburn describes the habit as "swinging in the rain" - males become more attractive to females when they are wet.

"They get sexier in the rain. Most males are like the females - drab and brown - prior to the breeding season but then adopt this brilliant blue plumage.

"While they are blue, they are strutting their stuff and females like the male then."

On top of the sexual turn-off prompted by global warming, chicks in their nests - nestlings - find it harder to survive in the rising dryness. "They are shrivelled like raisins," according to Professor Cockburn.

He and his colleagues go into the National Botanic Gardens just after dawn, before the gardens open to the public.

They erect a net and shoo the birds towards it. When the birds are caught, the scientists put tiny rings around their legs to they can be tracked once they've been freed.

It's a continuation of a 30-year study.

The caught male. Picture: Steve Evans

The caught male. Picture: Steve Evans

Normally they would find and ring 300 young birds a year. In the previous worst drought, the number of young fell to 200 but that has now fallen still further to 145 last year and around 95 this year.

In other words, the population is declining dramatically.

"The system is being hampered because once it becomes dry in the winter cold, the males say 'I'm not going for it this season'," Professor Cockburn says.

He says that if the conditions aren't right - and they are increasingly not right with global warming - the males postpone turning their plumage blue in the hope, as it were, that next year will be better.

Professor Andrew Cockburn and one of the birds he caught. Picture: Steve Evans

Professor Andrew Cockburn and one of the birds he caught. Picture: Steve Evans

Except that relentlessly rising temperatures mean that each succeeding season is unlikely to offer more benign breeding conditions.

"Things are going wrong, suggesting that fairy-wrens are a 'canary in the coal mine' for the effects of climate change," Professor Cockburn says.

It's not just the superb fairy-wren that is being hit. Plants are, too, he says.

"Our results suggest that our native fauna may already be experiencing an apocalyptic catastrophe, without even considering bushfires."

This story Why global warming is such a turn-off for Canberra's favourite bird first appeared on The Canberra Times.