Climate change has brought in marked shifts in the timing of egg laying by great tits in response to climate change within the same woodland and that this variation is linked to the health of nearby oak trees, according to a new study from Oxford University.
The researchers said that great tits in the UK lay their eggs around 14 days earlier than they did in the 1960’s. “As a result, these song birds are keeping pace with the other members of their food chain – winter moth caterpillars and the oak trees on which these insects feed – which have also advanced their spring timing in response to climate change over recent years,” the study said.
The study, titled ‘Spatial variation in avian phenological response to climate change linked to tree health’ is published in the journal Nature Climate Change.
Dr Ella Cole, Oxford University, who co-led the research noted; “Much of our understanding of how animals respond to climate change comes from studies that assume all individuals within a population experience the same environment. However, we know this is not the case, particularly for animals that are limited in how far they can travel from dependent offspring. Neighbouring individuals may experience very different environments. Studying these differences helps us understand what might limit the ability of animals to adjust to changing environments and therefore the scope for populations to cope with climate change.”
The researchers said that the analysis of breeding events from over 13,000 great tits over a 60-year time-span showed that the slowest nesting sites only advanced by 7.5 days, whilst the fastest sites advanced by 5.6 days. They claimed that this was linked to the health of the oak trees nearby the nesting site. The healthier the oak trees around the nest, the larger the advancement in timing a laying. Birds breeding in areas with healthy oaks advanced their laying by 5.4 days more than those breeding in areas with unhealthy oaks.
They carried out at the research at Oxford University’s Wytham Woods. They analysed data of 964 fixed location nest boxes, together with information on the health of 5,748 mature oak trees. Oak trees are much important to tits during the spring as huge numbers of caterpillars that feed on their foliage.
Dr Regan, Oxford University, who also co-led the work noted that the findings suggest that birds nesting in areas with poorer oak health are less able to keep up with the advancement of spring.