Early morning, Wytham Wood
This article caught my eye because it concerns the birds in a wood which is local to me - Wytham Wood, near Oxford, to which I have licensed access. This is reputedly the most intensively studied area of woodland in the world, belonging, as it does, to Oxford University.
Wytham Woods form an iconic location that has been the subject of continuous ecological research programmes, many dating back to the 1940s. The estate has been owned and maintained by the University of Oxford since 1942. The Woods are often quoted as being one of the most researched pieces of woodland in the world, and their 1000 acres are designated as a Site of Special Scientific Interest.Through intensive observation over successive years, researchers are able to measure changes in behaviour of species such as the Great Tit, Parus major with some of the best examples of observational biology in the form of research papers. For example, a few years ago a team of researchers showed that the British race of Great tits were diverging from their European relatives with changes in the beaks probably reflecting the fact that we in Britain provide feeding stations for birds to sustain them through the winter much more frequently than other Europeans, so the British Great tits are evolving so they can get the food in the bird feeders in British gardens.
The wooded parts of the Wytham Estate comprise ancient semi-natural woodland (dating to the last Ice Age), secondary woodland (dating to the seventeenth century), and modern plantations (1950s and 60s). The fourth key habitat is the limestone grassland found at the top of the hill. Other smaller habitats include a valley-side mire and a series of ponds.
The site is exceptionally rich in flora and fauna, with over 500 species of plants, a wealth of woodland habitats, and 800 species of butterflies and moths.
In the following article, ecologist, David López Idiáquez, a Postdoctoral Research Associate in Behavioural and Evolutionary Ecology, University of Oxford, explains how their research is measuring how Great tits are responding to climate change. His article is reprinted here from The Conversation under a Creative Commons license, reformatted for stylistic consistency, with photographs from Internet sources:
The great tits in this Oxford wood are adapting their breeding times as climate changes – here’s how
David López Idiáquez, University of OxfordAs part of a team of ecologists, I’ve been studying aspects of great tit biology at Wytham Woods near Oxford. One aspect of our research is how climate change affects their breeding behaviour. So far, our research suggests that these great tits have been able to deal with climate change effects.
During early spring, usually in March, great tits (Parus major) abandon their winter flocks and start preparing for the breeding season. First they find a mate and build a nest. Then they raise naked and blind chicks, each weighing a bit more than one gram, into fully feathered fledglings.
A lot of our research focuses on analysing great tit reproductive phenology – that’s the study and analysis of seasonal events such as plant flowering, bird migration and reproduction.
Phenological events are not fixed in time as they depend on environmental factors such as weather conditions. Thus, they vary from year to year. For instance, the earliest recorded start date for great tit breeding in Wytham is March 27. The latest has been April 24, almost a full month later.
Nowadays, the start of great tit breeding occurs more than 15 days earlier than it did in the 1960s. Our research suggests that great tits have successfully tracked the environmental changes imposed by climate change.
At Wytham Woods, spring temperatures have increased around 2°C since 1965. Despite the rising temperature, they are demonstrating what we call “phenotypic plasticity” – individual birds can adapt by producing different versions of the same trait in different environmental contexts.
The fluctuation in great tit breeding reflects climate conditions and food availability – notably, caterpillars of the winter moth, Operophtera brumata. These caterpillars are especially important when great tits are raising their chicks, which rely on these and similar caterpillars as their main source of food.
To maximise breeding success, great tits must synchronise the period of highest chick food demand with the peak of caterpillar availability. If they don’t, producing chicks has a much higher energetic cost because parent birds may have to fly further to collect food – this will probably result in fewer chicks surviving.
Great tit, Parus major
We record when these great tits lay their eggs, count the number of eggs laid and record how many chicks hatch, by regularly visiting the nest boxes. All birds breeding inside the nest boxes and their chicks are captured and marked with individually numbered metal rings. With an identification tag on each bird, we can build a detailed picture of their lives in the woods across successive breeding seasons.
Since then, methods have evolved and today, we combine the traditional approach with advanced technology including images taken from satellites and drones, and genetic studies to deepen our understanding of Wytham’s great tits.
By monitoring Wytham’s great tit population, scientists have been able to explore many different aspects of their biology, from the cultural transmission of song to the impact of age on mating behaviour and mate choice.
Early starters
We know that the great tits living here are responding to this rapid warming by adapting their life cycles. Climate change is also affecting winter moths. Data collected between 1960 and 2020 shows that their abundance peaks about 15 days earlier than it did in 1960.
This is probably why great tits have shifted their timing. By breeding earlier, great tits can stay in sync with the higher availability of caterpillars and meet the demands of their chicks, ensuring greater breeding success.
Do the seasons feel increasingly weird to you? You’re not alone. Climate change is distorting nature’s calendar, causing plants to flower early and animals to emerge at the wrong time.
This article is part of a series, Wild Seasons, on how the seasons are changing – and what they may eventually look like.
This article is part of a series, Wild Seasons, on how the seasons are changing – and what they may eventually look like.
We are investigating which environmental cues great tits rely on to time the onset of their reproduction. We are measuring variation in environmental factors such as temperature at very small scales. Since 2023, we have deployed 800 temperature recorders across the forest to record temperature variation with high spatial and temporal resolution.
We are also monitoring the phenological changes of trees, specifically the timing and manner of leaf development. Trees play a crucial role in this system, as they determine the emergence of caterpillars, and the timing and availability of food for the great tits.
Morning in Wytham Wood
Research at Wytham shows promising signs of great tits’ adaptability to climate change. However, it is crucial to remember that these observations come from a single population in an area experiencing a relatively mild climate.
Studies of other great tit populations, while reporting similar advances in the onset of reproduction to Wytham, suggest that these adjustments may not be sufficient to match the changes in the peak of food availability.
Climate change effects in wild animal populations are complex and diverse. Long-term data sets, such as the one available for Wytham Woods great tits, represent a valuable resource to shed new light on the causes, mechanisms, and consequences of population responses to climate change. Long-term monitoring projects like this one near Oxford are valuable tools that can be used, not only to understand and tackle current problems, but also future problems that we can’t yet predict.
David López Idiáquez, Postdoctoral Research Associate, Behavioural and Evolutionary Ecology, University of Oxford
This article is republished from The Conversation under a Creative Commons license. Read the original article.
Of course, any such observations in a local woodland like Wytham Wood will only be extrapolated to general conclusions if they are repeated at several separate locations, otherwise the operation of local factors could be distorting the findings.
For example, the observation that the British race of Great tits is evolving in response to bird-feeders in the UK compared to other European Great tits, would mean repeated observation and measurements in other UK woodlands and in multiple European woodlands, correlated with the sales of bird-feeders and bird food.
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