London, Europe Brief News – “In some parts of this wood, spring egg-laying has shifted by three weeks,” explains Dr Ella Cole of Oxford University.
The softly-spoken, seasoned ornithologist is showing me around a very special field site – Wytham Woods in Oxfordshire; one of the most studied woodlands in the world.
This year is the 75th anniversary of a study that has tracked 40 generations of great tits in the wood.
It is one of the longest-running animal-tracking studies in the world.
It is precisely because this is a 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 – that the data has revealed this trend in the timing of critical seasonal behaviour.
“The tits here are actually managing to track the other members of their food chain,” explains Dr Cole. “So, that’s the peak in the number of the caterpillars they feed on and in the timing of the oak trees [that the caterpillars] feed on.
“The whole sort of food chain has shifted earlier in the spring.”
These birds are relatively short-lived – with an average life span of just under two years – so 75 years of research has tracked 40 generations. “The human equivalent of that would be studying a family tree back to the 10th Century,” Dr Cole explains.
She and her colleagues have special permission to access the nest boxes, to mark each nestling and to ring every bird before it fledges.
The detail and longevity of the study has produced some remarkable insights.
