Victoria Gill is a science correspondent.
Egg-laying has shifted by three weeks in some parts of this wood.
The ornithologist is showing me around a very special field site, which is one of the most studied woodlands in the world.
The 75th anniversary of a study that tracked 40 generations of great tits in the wood is this year.
It is one of the longest running studies of its kind.
The data has revealed the timing of critical seasonal behavior because of the decades-long study that has followed every nestling, marking and counting the birds, recording the exact date that females lay their eggs and the date those eggs hatch.
The peak in the number of the caterpillars they feed on and the timing of the oak trees are what Dr Cole explains.
The whole sort of food chain has changed earlier in the spring.
Image source, Victoria Gill A study in numbers for 75 years.
The site was bequeathed to the University of Oxford by a local family in 1942.
Researchers have lived up to the bequest. In an area of about 800 acres, there are about 1,200 specially-built nest boxes, some of which have been occupied by blue and great tits.
There are nets hanging off branches to catch caterpillar and seed traps laid out beneath the canopy.
Image source, University of Oxford The great tit project is the longest running experiment in Wytham Woods.
The average life span of these birds is just under two years, so 75 years of research has tracked 40 generations.
She and her colleagues have access to the nest boxes to mark each nestling and to ring every bird before it flees.
The study has produced some amazing insights.
The UK's great tits have evolved longer beaks which appear to allow them to use bird feeders more efficiently, according to an evolutionary study that compared the UK's great tits with a population in the Netherlands.
In this country, we spend more on bird food than the rest of Europe, so it is easy to see how we might be causing evolutionary change.
Our changing climate has put a renewed focus on the evidence this project has provided about how the natural world is responding, allowing scientists to put all of the aspects of how a population of wild birds works in the context of climate change.
Prof Ben Sheldon from Oxford University leads the great tit project and says that they can ask how productivity and survival change over time.
The length of the study gives us more chance to observe extreme weather events that are seen as a risk of climate change.
A small group of researchers have the task of checking about 800 occupied nest boxes every spring. The timing of their busiest season becomes more unpredictable each year.
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