We study a broad range of topics relating to evolutionary biology, ecology and behavioural ecology. Our current research centres on four main areas:
(1) 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 5 decades, we have shown that the tits are now laying about 3 weeks earlier than they did in the 1960, inline with climate change (read more here: Great tits enjoying the warmer weather... so far, New Scientist). 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. Read more about this research here: Birds time breeding to hit 'peak caterpillar', Oxford Science Blog and on Ella Cole's research page.
(2) The Role of Social Processes in Evolutionary Ecology
One of the main focuses of our research at the moment 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 and disease 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 a grid of bird feeders, which are placed across the woods and open for two days every 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.
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).
Another area of social behaviour we are interested in is how tits learn from one another, and how new cultures spread through populations and persist over time. We do this by introducing 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 observing 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, and visit Lucy Aplin's research page.
Here are some additional news articles relating to our research on social behaviour:
- What happens when birds divorce?, Science Magazine
- Microchip tracking reveals how songbirds forage, Scientific American
- Early birds find worms for dinner, BBC Nature News
- Pilfering blue tits copy their friends to find lunch, Audubon
(3) 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.
Our collaborators on the great tit genetics project:
- Jon Slate: http://jon-slate.staff.shef.ac.uk/about-the-group/
- Martin Groenen: https://www.wageningenur.nl/en/Persons/prof.dr.-M-Martien-Groenen.htm
- Marcel Visser: https://nioo.knaw.nl/en/employees/marcel-visser
(4) 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.
News articles on more Wytham tit research:
- Clever birds don't have it all, Irish Times
- Bold birds show 'live fast, die young' attitude, Oxford Science Blog
- Animal Personality (audio), BBC Radio 4 Frontiers