Tiny British Bird is an Unlikely Climate Change Victor

By Elspeth Dehnert, E&E reporter
3/26/2014 10:44:12 AM

While climate change poses increasing risks to many species around the world, the U.K. long-tailed tit population is doing just fine -- in fact, it's thriving, according to scientists at the University of Sheffield.

New findings from a 20-year study of the tiny-bodied birds by professor Ben Hatchwell of the university's Department of Animal and Plant Sciences reveal that, contrary to popular belief, the biggest climatic impact on their survival occurred during spring, not winter.

Using individually colored leg rings, researchers tracked a number of the long-tailed tits in the Yorkshire, England, study to determine which individuals were present in the population at any one point in time.

They were then able to construct annual data on the adults' survival rates and examine the effect each of the four seasons' weather had on the population, explained Karl Evans, who is leading the recent work alongside doctoral student Philippa Gullett and British Trust for Ornithology ecologist Rob Robinson.

The long-tailed tit is easily recognisable with its distinctive colouring, a tail that is bigger than its body, and undulating flight. Gregarious and noisy residents, long-tailed tits are most usually noticed in small, excitable flocks of about 20 birds. Like most tits, they rove the woods and hedgerows, but are also seen on heaths and commons with suitable bushes. Found across the UK escept for the far north and west of Scotland. They can be seen in woodland, farmland hedgerows, scrubland, parkland and gardens. In winter they form flocks with other tit species. (Credit: Flickr/Bob McCaffrey)

"What we found was that adult survival rates were influenced by climate during the spring breeding season, which is probably because unfavorable climates mean the adults have to work much harder when they're rearing brood," said Evans.

Because the birds only live for two or three years, they only have a couple of opportunities to produce and raise chicks, resulting in an intense determination to fulfill their reproductive mission that can sometimes strain them to the point of death -- a scenario that is more likely to occur in colder temperatures.

"If it's cold and wet in spring, that makes their job much tougher," Gullett said in an official statement. "Food is harder to find; eggs and chicks are at risk of getting cold."

Basically, warm springs equal a more flourishing long-tailed tit population, which is why the United Kingdom's recent spring warming is likely correlated to the birds' increased survival rate, according to the study. Warm autumns were found to have a similar effect.

Beating climate change

But guaranteeing that the seasons have a positive impact on the birds' survival comes down to more than just temperature; precipitation plays a role, too.

"Rainfall has quite a strong impact on survival rates," said Evans. "It's not just about temperature. Therefore, when we're looking into climate change, one has to consider a wide range of parameters to really understand what the effects are going to be."

Although future climate change predictions show increases in spring and autumn precipitation at the long-tailed tit population study site, the seasons' higher temperatures will override the negative impacts from any potential rise in rainfall levels, the study notes. This indicates that the tiny British birds will thrive under future climate change.

"We've got very good estimates under a range of climate change scenarios for what the future climate will be in the study location," Evans said. "And those models suggest that survival rates are going to continue to increase in the future."

Reprinted from ClimateWire with permission from Environment & Energy Publishing, LLC. 202-628-6500.

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