Great tits enjoying the warmer weather so far 19:00 08 May 2008 NewScientist.com news service Mason Inman
As climate change forces animals to shift their breeding schedules, one group of British birds has been able to quickly adapt to the warmer weather without having to rely on slower evolution. There are limits to their flexibility however, and when those limits are reached, global warming could hit the population hard, researchers say. Since 1961, ecologists have been tracking the population of great tits that breed in Wytham Woods, near Oxford, UK. "It's only in the past 30 to 35 years that you see this increase in temperature in early spring to which the birds have responded," says study leader Ben Sheldon of the University of Oxford. The birds now lay their eggs 2 weeks earlier than they did in the 1970s, tracking a 2-week shift in the emergence of their favoured food the caterpillars of the winter moth. Like many insects, the caterpillars' development is triggered by temperature. "The birds are timing their breeding to match the abundance of food," Sheldon says. Plastic limit The birds have shifted their breeding times through an in-born flexibility, or plasticity, which means they can maximise the chances of their chicks' survival. One sign that plasticity is behind the shift, rather than evolution, is that the birds seem to respond to a warmer spring by laying their eggs earlier in the same year. You would get a lag with evolution, because it takes a generation or more to have an effect, Sheldon says. "It wouldn't manage to keep track so closely." The British birds have done well, with their population growing. But as temperatures continue to rise, if the birds reach a limit of how far they can plastically adjust, natural selection could kill off many of the birds, Sheldon says. That's what has happened in the Netherlands with warmer temperatures, natural selection has taken its toll on a population of great tits there, says Marcel Visser of the Netherlands Institute of Ecology in Heteren. Breeding rule It's striking that the Oxford birds have enough plasticity to adapt to climate change, Visser says. The difference might be because, around Oxford, both the early spring and late spring have warmed up, while in the Netherlands the early spring has not warmed much. So it looks like all the birds are following a rule "breed earlier in warm years" that doesn't work well in the Netherlands, Visser says. "It's kind of a coincidence that the rule the Oxford birds use happens to work," he adds. The great tits in the UK may be an exception, Visser says. More generally, animals seem to be following out-of-date rules. "It's a very general pattern that many animals use rules that are no longer optimal because of climate change," he says. Journal reference: Science (DOI: 10.1126/science.1157174); -- "A little rudeness and disrespect can elevate a meaningless interaction to a battle of wills and add drama to an otherwise dull day." ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~| Adobe® ColdFusion® 8 software 8 is the most important and dramatic release to date Get the Free Trial http://ad.doubleclick.net/clk;192386516;25150098;k Archive: http://www.houseoffusion.com/groups/CF-Community/message.cfm/messageid:259984 Subscription: http://www.houseoffusion.com/groups/CF-Community/subscribe.cfm Unsubscribe: http://www.houseoffusion.com/cf_lists/unsubscribe.cfm?user=89.70.5
