Some of our best-loved species are changing their breeding cycles and heading north in their fight for survival in a warmer world. Stephen Moss, the Guardian. January 2021.
Pic: Regine Tholen, Unsplash.
Lockdown has sparked a renewed interest in our garden birds, with millions of us enjoying watching them from our windows. But could some species – including the common and familiar great tit – vanish from Britain’s gardens by the end of the century?
Researchers from the Norwegian University of Science and Technology, working with the University of Oxford, have modelled how great tits are reacting to the climate crisis. Specifically, are the birds able to respond to the earlier emergence of the caterpillars on which they feed their chicks?
Birds such as great tits have evolved to time their breeding cycle so it coincides with the peak of moth caterpillars that feed on oak leaves, which traditionally happens in late May and June. But as temperatures rise, so oaks are coming into leaf earlier, and the caterpillars have responded by hatching out earlier too.
This means that when the great tit chicks are ready to be fed, the peak of caterpillars is already coming to an end. Because the parent birds need to find 1,000 caterpillars every day for their hungry offspring, any mismatch is likely to dramatically reduce breeding success.