© Andrew Crystal
Great tits in England are laying eggs about two weeks earlier than 47 years ago a study has found, showing that they are adapting well to climate change.
Since 1947 more than 80,000 great tits have been ringed in Wythan Woods, near Oxford although this study has only used data starting from 1961. What is thought to have been the longest running study of ringed wild animals anywhere in the world has shown that our great tits have adapted so that their chicks hatch when there is an abundance of winter moth caterpillars.
Once great tits hatch they are fully grown and fledged in two weeks and because they grow so quickly they need a readily available food source and as there are usually 8 or 9 chicks per brood it also needs to be an abundant one. During this two-week period each chick needs to eat around 70 caterpillars per day and being able to synchronise the timing of hatching with the emergence of the caterpillars is crucial to their survival.
The caterpillars’ emergence is triggered by ambient temperatures and in order to have chicks hatch at the right time it is believed that great tits begin their breeding cycle in response to temperatures.
Although it is good news for great tits that they are able to be so flexible in response to climate change, the RSPB and other conservation bodies warn that this does not change the fact that climate shifts could have devastating results for other species. For instance they believe that climate change is the most likely factor for the dramatic decline of some sea bird colonies around the British coast.