by: Lewis Smith, Environment Reporter
British great tits have proved themselves to be far more adaptable to climate change than their counterparts in the Netherlands.
In the past half century the great tits living in Wytham Woods (also known as the Woods of Hazel) near Oxford, have brought forward the date that they lay their eggs by an average of two weeks. The advance is a response to climate change and the timings of the egg-laying showed that the birds tracked the variations in temperature.
The British great tits, Parus major, were also able as individuals to respond to fluctuating temperatures from year to year and are the first species to demonstrate such an ability. Because they reacted individually to temperatures, which controlled the availability of vital food, they tended to choose the same time to lay their eggs.
Dutch great tits, by contrast, have been shown by previous research to be able to respond as a species only by using a scattergun approach to laying times and relying on natural selection to weed out those who laid too early or too late.
They showed a much weaker overall response to changes in the climate and the average change in laying time was several days less than the British birds. The change in laying times exhibited by the tits in Britain and the Netherlands was linked to the availability of winter moth caterpillars, Operophtera brumata.
Ben Sheldon, of the University of Oxford, said that the British birds had, so far, been able to “take climate change in their stride”. But he said that the difference between British and Dutch responses was surprising because as the same species they would have been expected to behave in much the same way.
“They are the same species. You would think of them as being pretty much interchangeable yet for some reason there’s a close tracking of the environment here but not in Holland,” he said.
“The British ones seem to be adapting better to climate change. They are showing a more appropriate response.
“The whole population seems to do the right thing. In the Dutch population fewer are doing the right thing so they aren’t doing as well. In the UK this population is doing absolutely fine.”
The study, published in the journal Science, was carried out by researchers from the University of Oxford, the University of Edinburgh and the Unite Mixte de Recherche in Montpellier, France.
Almost 10,000 records of great tits that have bred in Wytham Woods over the past 47 years were used for the study.
Great tit parents raise an average of eight chicks in each nest, though they can successfully raise as many as 15 in one go. The chicks leave the nest little more than two weeks after hatching and grow so fast that the parents have to catch about 500 caterpillars and other insects every day to feed their young.
“Having that many kids at the same time does go hand in hand with not living very long,” Professor Sheldon said.
The reason for the difference in how the British and Dutch birds adapt to the changing environment is a mystery.