Global warming is causing great tits to hatch a month earlier than they did 75 years ago due, a long-running study revealed.
Scientists working on one of the longest studies of animal populations in the world discovered the first great tit egg of spring was laid exactly four weeks earlier than the first of the research in 1947.
Experts said the finding reveals how spring has moved forward a whole calendar month over the time of the study, conducted at the University of Oxford’s ‘living laboratory’.
The Wytham Woods’ Great Tit research is the longest continuous study of an individually-marked animal population in the world.
For more than seven decades, scientists monitor the timing and size of the population of the birds commonly found in many gardens around Britain.
It plays a key role in scientists’ understanding of how populations change in response to the environment – particularly how they are coping with changing climates and rising global temperatures.
Sir David Attenborough, who has visited the ‘living woods’ in the Oxfordshire countryside many times over his long career, praised the study’s ability to help increase the understanding of the natural world.
He said: “I am delighted to hear of the 75th anniversary of the long-term great tit study in Wytham Woods.
“Having visited several times, I know how fundamental this study, and others like it, have been for our understanding of the impacts of climate change on the natural world.
“Long-term studies like this require long-term commitment, and I wish the study – and its practitioners – a long and productive future.”
Like many aspects of their biology, the timing of the laying of great tit eggs is influenced by large and small-scale factors, such as climate, social interactions, and the health and behavior of nearby trees, scientists said.
Researchers are beginning to understand these factors in terms of potential vulnerabilities and resilience to changing climates, the experts said.
Professor Lord John Krebs, Emeritus Professor of Zoology at Oxford, and a member of the House of Lords Science and Technology Committee said: “In the late 1960s, when I started my DPhil [the Oxford equivalent of a PhD] on the Great Tits in Wytham, there was a remarkable ‘long-term’ record of the population, which I analyzed to understand what factors determined the number of birds in the population.
“At that time ‘long term’ meant about 20 years. Now, thanks to the foresight of those who started the study, and many generations of field workers, there is a truly unique record which will continue to yield novel and important insights into the ecology and behavior of bird populations in the wild.”
Tits make excellent study species for ecological research as they readily take to nest boxes, breed at high densities, do not travel far from where they are born, and cope well with being monitored by scientists.
Scientists can individually tag large numbers of nestlings with unique leg rings and follow them throughout their lifetimes.
Currently, researchers use breeding data from 1,209 fixed-location nest boxes in this Site of Special Scientific Interest to the west of Oxford, together with information on many other aspects of the ecology of Wytham Woods, collected by other scientists based at the University of Oxford.
As the study has developed it has increasingly made use of new technology, including electronic tags, remote-sensing, and genome analysis to understand evolution.
Professor Ben Sheldon, who leads the Wytham Great Tit study, said: “A study of this duration is built on the work of hundreds of people, and it’s been a great privilege to build on their dedication year in, year out, to continue the study.
“That continuity has enabled us to use many decades of data to understand how changes occur over time.
“One of the most striking changes is that the average great tit breeds three weeks earlier now than it did at the start of the study.
“This shift is a clear signal of the effects of climate change on one of our most familiar woodland and garden birds, and it is studies of this kind that allow us to work out what the consequences of such changes have been, and what they may be in the future.”
More than 70 Ph.D. theses have been completed on this project and over 350 scientific papers published.
Five particularly significant discoveries from the great tit study over the last 75 years include that climate change is having clear effects on familiar biological systems and that Birds adjust their behavior plus their reproductive decisions so that they produce optimal traits for their specific circumstances.
It also revealed that individual birds can learn complex behaviors from each other and this can lead to the emergence of cultural differences as well as that evolution can occur over surprisingly small scales in space and time, even in birds.
How social networks connect birds across the whole population, but individual birds adopt very consistent positions in those social networks, was another discovery made as part of the research.
Researchers said they know that climate change is driving large-scale alterations in the timing of seasonal events, affecting plants and animals across the globe.
But researchers at Oxford are keen to know how much does this matter for the survival and reproduction of these organisms and ultimately how they will be affected by climate change?
New research, funded by an ERC Advanced Grant awarded to Professor Sheldon, aims to combine measures of the timing of when leaves are produced for hundreds of thousands of trees across the University of Oxford’s Wytham Woods, with data on insects and birds that rely on these trees for food.
Oxford’s researchers are aiming to work out how much birds are influenced by effects at small and large scales and how these interact in ecological networks.
The researchers at Oxford University’s Department of Zoology hope the next 75 years of study will be as productive and influential as the first seven-and-a-half decades.
