Tim Birkhead tells Karin Ranero Celius about promiscuous birds and teaching science students.

“Be thou like the dunnock – the male and female impeccably faithful to each other,” said Reverend Frederick Morris in 1853. In an attempt to preach fidelity, he encouraged his parishioners to behave like dunnocks (Prunella modularis) – small, brown, rather plain-looking birds. Far from being monogamous, however, the dunnocks – from a Victorian point of view – have shockingly lax morals, with the female often mating with several males. What would Reverend Morris have made of the scandalous truth?

Indeed, rivalry between males and discrimination by females extends beyond the sexual act itself. Inside the female, the sperm of different males fight for supremacy – this is sperm competition. At the same time, the female may be able to select the sperm that are best for her – this is sperm choice. This is the true battle of the sexes. The males and females of each species are permanently locked in a struggle to out-evolve each other, as their reproductive anatomy and behaviour change to achieve their conflicting aims: maximum fertilisation versus best fertilisation.

These radical ideas were just beginning to emerge when Tim Birkhead graduated from university in 1972. “I just feel incredibly fortunate to have been the right age, at the right place and the right time,” he says.

Tim’s initial interest was in sea birds. In 1972, he started a project to monitor guillemots on Skomer Island, a nature reserve in Wales: he looked at the adult and immature survival rates and the age of the first breeding and reproductive success, as well as assessing the effects of oil pollution and climate change on the population. Although the project continues and he returns to Skomer Island regularly, the focus of his research gradually moved towards sex. In particular, post-copulatory sexual selection.

Tim Birkhead’s research has helped to re-shape our understanding of bird mating systems. Why should a bird or an individual copulate with more than one partner? What determines which male fertilises the female’s eggs when she has mated with several partners? And how are sexual conflicts resolved? His research involves finding out what happens to the sperm of the male inside the female’s reproductive tract and investigating the importance of sperm competition and sperm choice in determining which male fertilises the eggs.

In his ongoing quest to explore the nature of sexuality, Tim Birkhead could be considered a paparazzo of nature – travelling to remote islands and bearing extreme discomfort in the hope of catching birds mating, and when they do, splashing their most intimate details and pictures over the pages of science journals.

Tim’s passion for birds goes way back – to when he was 11. “On one memorable holiday in Wales, my father took me to a little island called Bardsey Island – one of the most beautiful places in the world, with lots of wonderful birds. As we walked back at the end of the day, a young man sat looking through a telescope with a notebook and my dad just looked at me and said: ‘You could do something like that when you get older’.” And he did.

But Tim is not always the observer; often, he is the one in the spotlight. A good scientist must be able to communicate his research and engage audiences by making it relevant and Tim does just that: he illustrates science with many stories, and he’s clever, funny, persuasive and very clear. In fact, he is one of those teachers whose lectures should be scheduled early in the morning to make it worth the students’ while to get out of bed. What makes his lessons so special? His enthusiasm is surely part of the answer.

Doing science is important, but so is understanding science itself. “The history of science course that I teach is about doing science and what it means to be a scientist. I try to teach it in an unconventional way: I don’t let my students take notes because I want them to listen, to be inspired by what I tell them and then go off and do the necessary reading. For one of the major assessments, I take them to a place where, based on their reading and a quote I give them, they have to organise a conference for the day. It’s up to them entirely how they interpret it, and how they give the presentation, and everybody does it very differently. They learn about the history of science by listening to their peers.”