A tough winter has taken its toll on Canberra's bird population, with less than half of the superb fairy-wrens that live in the Australian National Botanic Gardens surviving, researchers from The Australian National University (ANU) have found.
ANU biologists have been monitoring the birds by recording their presence weekly since the late 1980s and say this year has seen the largest loss recorded in any one winter.
"We had 72 adults and 39 chicks at the end of last summer. Of these, 37 adults died - or 51 per cent - and there's only six remaining chicks," Associate Professor Damien Farine said.
"It's a big loss. To put it in perspective in 1999, 2002 and 2003 we lost about 20 per cent of the adult birds and those were exceptional years."
According to Associate Professor Farine, a sharp change in temperature might be partially to blame for the high mortality rate.
"We had quite a warm start to winter and then it got cold quickly. Previous modelling on this population of superb fairy-wrens found that there was quite high mortality in the weeks after a winter heatwave," he said.
"The birds need lots of still, sunny winter days, as that's when they replenish their energy and survive the cold nights. But this sometimes leaves them unprepared for a very sudden turn of cold weather.
"We've seen widespread reported declines of woodland birds in Australia over the past few decades. This population is no exception. It was already down by about 65 per cent when compared to the long-term size of this population, and now it's crashing further. It is crazy to think that we might be seeing the population make its way towards extinction."
Associate Professor Farine and his ANU colleagues will continue to monitor the birds in the hopes of a successful upcoming breeding season.
"They do sometimes rebound. If food sources are good during the spring and early summer, you might see a big boom," he said.
"What observations like this prove is the value of studying a population like this where we track the fate of individuals over a long period of time. Every individual in this population is uniquely identifiable, so we can pinpoint when each mortality event happens and what the birds were doing beforehand.
"The data brings an important perspective on how changes in the climate over the winter is impacting our bird populations, and is something that we hope to study in much more detail over the coming years."
Another group of birds monitored by ANU experts at Campbell Park, in the foothills of Mount Ainslie, showed a 70 per cent mortality rate.
"It's not just happening in one place. It's as bad, if not worse, elsewhere," Associate Professor Farine said.
