Our Research

 

We study a broad range of topics relating to evolutionary biology, ecology and behavioural ecology.  Our current research centres on four main areas:

The Ecology of Spring Timing

Tits produce large broods of young compared to most bird species. They are able to do this because they utilise the superabundance of caterpillars that hatch in deciduous woodlands every spring. However, this caterpillar peak is short-lived - caterpillars hatch out when the leaves of trees, such as oaks, begin to unfurl, but can only feed on young leaves, meaning they will only be available to the birds for a couple of weeks. When birds should start laying their clutch is therefore a crucial decision - if parents get it wrong, and lay too early or too late relative to the peak in caterpillar availability, they may not be able to find enough food to keep their brood alive.

Using our tit breeding records spanning the last 6 decades, we have shown that the tits are now laying about 2 weeks earlier than they did in the 1960, inline with climate change (read more here). However, our recent research has revealed that this shift in the timing in response to climate change varies considerably across the woodland with the slowest nesting sites only having advanced egg laying by 7.5 days, whilst the fastest sites advanced by 25.6 days. This variation is linked to the health of nearby oak trees - birds breeding in areas with healthy oaks have advanced their laying by 5.4 days more than those breeding in areas with unhealthy oaks (read more here).

Our current research focuses on understanding the complex interactions between trees, caterpillars and tits to shed light on how birds time their breeding attempts, and the consequences of these decisions in different environments and at different spatial scales. We are also interested in the extent to which birds may use social information to time their breeding, as well as how birds manage trade offs between different life history traits (e.g. number vs. quality of offspring) in the face of climate change (see Carys Jones and Anett Kiss’ research pages for more details).



BBC Springwatch featured some of our research exploring the importance of spring timing for tits

Our research on incubation behaviour featured on ‘Attenborough’s Wonder of Eggs’

Sir David Attenborough visits Wytham and talks about the importance of spring timing

PhenoScale: The Importance of Spatial Scale for Ecological & Evolutionary Processes

We know that climate change is driving large scale changes in the timing of seasonal events, affecting plants and animals across the globe. But how much does this matters for the survival and reproduction of these organisms, and ultimately how they will be affected by climate change? The central premise of a current UKRI-funded 5-year project awarded to Ben Sheldon is that a major reason for that lack of understanding is that we haven’t focussed enough on the right spatial scale. By combining measures of the timing of leaf-out for hundreds of thousands of trees across Wytham Woods, with data on insects and birds that rely on these trees for food, we will be able to work out how much the effects of climate change are driven by effects at small and large scales. 

We fly WingtraOne GEN II drones carrying multispectral cameras (MicaSense RedEdge-P) repeatedly over Wytham Woods thoughtout spring to capture vegetation phenology at the scale of individual trees. Images are stitched to create NDVI orthomosaics for the entire woodland. Central image shows an NDVI orthomosaic for a single flight in late March 2023, before most trees had come into leaf. Right-hand image shows an individual oak crown. Image ground sampling distance was ~3 cm / pixel, flying at ~100 m agl.

The timing of leaf-out in deciduous woodlands can vary greatly over small spatial scales. We hypothesis is that this small-scale phenological variation will promote ecological and evolutionary diversity, enables community stability & buffers populations against large-scale climatic variation.

We plan to develop novel methods to characterize scale-dependent phenology of primary producers and match this with multi-decadal phenological data from primary and secondary consumers.

We plan to use this platform to address four additional research objectives:

  1. Quantify how scale-dependent phenology drives selection and co-evolution between species in different trophic levels

  2. Determine how scale-dependent phenology influences community structure and stability across trophic levels

  3. Explore how behavioural flexibility of consumers enables exploitation of phenologically variable landscapes

  4. Quantify how climatic variability and scale-dependent phenology interact to influence the demographic resilience of populations

The Role of Social Processes in Evolutionary Ecology

One of the focuses of our research is to better understand the causes of individual variation in social behaviour and the consequences of social structure for a range of processes, including information spread.

How individuals interact with one another is likely to have important consequences for their lives. Through tracking the activity and movements of thousands of individual birds in Wytham, we can monitor the social interactions within winter feeding flocks. We do this using “smart” bird feeders, which are put up in the woods and open for two days a week. Each feeder has RFID tag readers that detect every tagged bird that comes to feed. This gives a snapshot of who is feeding with whom, allowing us to test how individuals differ in their social behaviour, who they form strong social bonds with, and how the environment shapes their societies.

Measuring social behaviour: each black dot here is a bird feeder fitted with detectors that will record a bird's identity every time it lands to feed. This tell us which birds are feeding together. We open these feeders for two days a week throughout autumn and winter, allowing us to closely monitor the birds' behaviour across the seasons.

In addition to observing the birds, we conduct field experiments, such as using “selective feeding systems” that allow the automatic control of which birds are allowed to feed together. Through using this approach we have shown that social connections formed during foraging carry-over into other contexts, and also that mated pairs who hold strong social relationships will shape their activity, social network position and foraging strategies around each other. To learn more about this research see the following articles: The great tit chooses love over food, Scientific America and Feathered friends for life...or not, Audubon and Josh Firth's research page. We also find that how birds interact with one another relates to their personalities (see video below and article here: Shy great tit birds flock together, National Geographic). We currently have several postgraduate students researching the role of social processes in ecology and evolution, covering topics such as cooperation, leadership, the fitness consequences of social relationships, and age assortative breeding (see Joe Woodman’s research pages for more details).

Josh Firth talked about some of his research into social behaviour

Another area of social behaviour we are interested in is how tits learn from one another, and how information spreads through populations and persist over time. One way we have done this is to introduce new traditions into a population (by training individual demonstrators to open puzzle boxes containing food and releasing them, along with multiple puzzle boxes, into the wild) and observe how these traditions spread through groups. To learn more about this research watch the below video, read article here: Scientists instil new cultural traditions in wild tits, National Geographic, listen to podcast here. One of the main focuses of our research at the moment is how the social environment (e.g. population density and stability) influence how both simple and more complex information spread between individuals (see recent research on this in the publications tab).

Lucy Aplin talks to BBC Winterwatch about her work on social learning in great tits

Tits have complex social lives, and their songs and calls play an important role in them. In particular, their deceivingly simple songs—which they use to attract mates and deter rivals—hide great diversity: in Wytham alone, great tits sing perhaps over a hundred different ‘song types’. These song types must be learnt from other birds early in their life, which creates fascinating cultural dynamics.

Our work with the songs of the Wytham tit population aims to explore their ‘cultural landscape’; and to use it to study the complex interaction between ecology, population processes and cultural evolutionary dynamics. We hope to gain a better understanding of cultural diversity in bird song: from the repertoires of individual birds to the complex dynamics that emerge at the level of interacting populations. To do this, we have been collecting (2020—present) a longitudinal dataset that brings together detailed information on life-history traits, adult characteristics, and complete song repertoires of hundreds of individually marked birds. See Nilo Merino Recalde’s research page for more details.

Here are some additional news articles relating to our research on social behaviour:


Quantitative & molecular genetics

For almost any characteristic of wild animals and plants that we can measure, we observe variation. Why do individuals differ from one another? One of the ways to answer this question is to use different kinds of genetic analysis to work out how much variation is due to the environment, and how much due to genetic differences between individuals. Tits have been a very suitable species to try to do this sort of work, particularly because it is easy to match together parents and their offspring by simply catching and identifying parents, and by ringing nestlings at the nest. 

One of the classic approaches to this question is called quantitative genetics. This refers to an approach where it is assumed that traits are influenced by many genes that each have very small effects. By working out what proportion of genes we expect to be shared between different kinds of relative (e.g. parents and offspring share half their genes; first cousins share only one eighth of their genes) and comparing how similar their phenotypes are, we can estimate the relative importance of genetic versus other kinds (e.g. environmental) of variation. Such work has been a particular focus over the past decade or so, but one of the earliest estimates of the heritability of a trait in a wild animal population came from Wytham great tits, with Perrins & Jones study of clutch size heritability in 1974.

More recently, together with collaborators elsewhere (Jon Slate in the UK, and Marcel Visser and Martin Groenen in the Netherlands) we’ve been developing molecular genetic tools to study the genetics of traits. This has involved genotyping large numbers of birds at hundreds of thousands of genetic locations that are polymorphic within the study populations. Together with other scientists studying great tits across Europe we have also taken this one step further and sequenced the genomes of great tits across many populations (see map below). Work is still underway analysing this variation, but two of the early findings are, first that over much of Europe there is very extensive mixing of genes between different locations. Second, this work has enabled us to test the assumptions of quantitative genetics, and we do indeed find that most traits that we test seem to be influenced by many genes of very small effect.

Recent work on this project has revealed that a genomic regions under selection contained genes that explained variation in bill length. Variation in this gene was related to reproductive success in the Wytham population but not the Dutch population, with birds with the long bill variant producing more fledglings than birds with the short bill variant. Bill length, and the associated genetic variation, was also linked with usage of bird feeders, raising the possibility that longer bills may have evolved in the UK as a response to supplementary feeding, which is more extensive in the UK than in mainland Europe (read more here).

Sites of great tits that have been analysed for variation in the genome (see Laine et al. 2016, Nature Communications).

Our collaborators on the great tit genetics project:

 

Ecology and Epidemiology of Avian Diseases

In recent years we have broadened our understanding of the tits in Wytham by considering the way that infectious diseases spread among, and affect, the different tit species. One disease that some find surprising to learn infects birds in the UK is malaria. Far from being a largely tropical disease as in humans, avian malaria can be found in birds in very many parts of the world. There are several different types of malaria parasite, but one group - Plasmodium - is quite closely related to the parasites that cause human malaria (there is no danger of humans becoming infected by bird malarias however!).  Focussing particularly on blue tits, and to a lesser extent on great tits, we have explored when and where malaria infections occur and what effect they have when then do so.

One surprising finding is that, for tits in Wytham, whether they are infected depends hugely on where they live. Although the overall infection rate is about 40% for blue tits and about 60% for great tits, there are parts of Wytham where fewer than 10% of birds are infected and other parts where more than 80% are. This variation is very stable from year to year, and occurs over short distances: as little as 1 km separates the areas with highest and lowest infection rates.  Our best hypothesis for the cause is that it reflects the distribution of the vectors of malaria: bird-biting mosquitoes. Because malaria infections affect the survival rate of the birds, the different rates of infection in different parts of the woodland lead to variation in survival rates in different parts of Wytham Woods.

A second disease that we have worked on was a novel outbreak of avian pox among birds. Infecting mostly great tits (and to a lesser extent other tit species), this infection, caused by a pox virus, was first noted in the UK in Surrey in 2006. It spread rapidly through England and reached Wytham by 2009, and by 2010 almost 10% of birds showed symptoms. Alarmed by this, we obtained an Urgency grant from NERC to study this new disease together with  colleagues at the Institute of Zoology.  Our studies, which were aided enormously by records from the public of birds in gardens, documented the spread of this disease as well as showing that it had serious effects for infected birds. Thankfully, the infection rate seems to have declined, at least locally, though we still find occasional records of infected birds.

Shelly Lachish speaks to BBC South Today about avian pox in Wytham Woods