Undiminished passion

Tim Birkhead

My career in sperm competition has been a roller-coaster ride, energised by a number of particularly special moments. One occurred while I was studying guillemots Uria aalge on a group of uninhabited islands off the coast of Labrador in the early 1980s. Surrounded by sea-ice, magical auroras, humpback whales Megaptera novaeangliae and thousands of promiscuous birds, this was a wonderful study site. Plotting the results from my notebook at the end of one day, I became aware of what at that time seemed like a remarkable emerging pattern: extra-pair copulations were occurring exactly at the time in a female's cycle when they were most likely to result in fertilisation. It was one of those extraordinary moments when it was clear that everything was going to work out. Not only would this be (at that time) one of the most detailed studies of extra-pair behaviour in birds, it would also suggest that extra-pair copulations were adaptive (Birkhead et al. 1985). DNA fingerprinting was still a few years in the future, so it would be a while before we knew how this pattern would impact on fitness, but the behaviour was clear, and at the time my results seemed tremendously exciting. Importantly, they also raised many new questions. My obsession with seabirds, islands and sex, however, had started long before I went to the Arctic.

Like many of my generation of behavioural ecolo-gists, I was a fanatical naturalist as child, encouraged by my father, a keen birdwatcher, and my mother, an accomplished artist. I was indulged - as a teenager I kept birds in my bedroom, whose walls (and carpet, inadvertently) I painted in my own designs. My mother fostered my enthusiasm and my father instilled in me two traits that today might seem old-fashioned: a strong work ethic and always to do my best. We lived in northern rural England, outside Leeds, and with a freedom almost unknown today I spent many days bird-watching alone or with friends. My life revolved around natural history: I raised young magpies Pica pica, rooks Corvus frugilegus, tawny owls Strix aluco and starlings Sturnus vulgaris. I collected insects and was the proud owner of an aviary of foreign birds. When I was 12 during a family holiday in north Wales I was taken by my father to Bardsey Island for the day. It was almost surreal in its perfection: thrift-covered cliffs, an azure sea and cerulean skies full of choughs Pyrrhocorax pyrrhocorax. As we walked across the island towards the end of the day we saw a young man sitting with a telescope and a notebook studying birds, and my father casually said to me, 'You could do something like that' - little realising how prophetic his comment was.

At school I was uninterested in (and therefore pretty useless at) everything except biology and art, frustrated at being imprisoned when I could have been outdoors. Maths, physics and chemistry were difficult because they were too abstract: I liked art and biology precisely because you could see them. I was encouraged and inspired by one or two extraordinary teachers - the combination of not finding all school-work easy, together with seeing how valuable good teaching could be, later made me aspire to be an effective teacher myself.

At about 17 I started to 'study' the grey heron Ardea cinerea, a species, like the peregrine Falco peregrinus and other raptors, whose numbers had been reduced by toxic chemicals. I knew I wanted to study herons, but with no guidance, I had no real idea of what to do. My 'studies' consisted of watching the birds at a daytime winter roost near Farnley Park, a beautiful estate where 150 years previously J. M. W. Turner had painted landscapes, herons and other birds. I spent entire winter days huddled in the undergrowth watching these majestic birds, elated by the occasional flurry of raised plumes as birds disputed the best roost location. If nothing else, my heron-watching honed my observational skills and powers of endurance.

I went to Newcastle University to read zoology in 1969 and loved it. My most inspiring teacher there was Robin Baker, who told us about the then unpublished work of Geoff Parker and Bob Trivers on sperm competition and sexual selection. Hearing about this and seeing the logic of individual selection for the first time was an extraordinary moment. I was inspired, and decided there and then that I would pursue the study of sperm competition in birds.

During one university vacation I worked on a relative's farm in Cornwall. Knowing of my interest in herons, he told me that an old school friend of his, Ian Prestt, was investigating the effect of pesticides on herons and other birds at Monks Wood Experimental Station. A letter secured me an invitation to experience this research first hand, and before I knew it I had the keys of a Land Rover and was allowed to study the herons' social behaviour on my own. It was exhilarating. I felt I was doing something constructive, and it was great to be able to come back each day and enthuse about what I had seen. At Monks Wood I met John Parslow, who later offered me a vacation job looking at guillemots on Skomer Island, Wales.

John was also interested in the effects of toxic chemicals on seabirds, and found an excuse for me to go to Skomer.

Before that, I attended the Edward Grey Institute student conference in Oxford in the spring of 1972. David Lack was director of the EGI, and he asked the gathered group of students if anyone was interested in undertaking a DPhil. He preferred to walk rather than sit, so my 'interview' took place walking up and down outside St Hugh's College in light rain. I babbled on about my interest in individual selection, social behaviour and sperm competition, and Lack, who didn't say much, merely commented that he knew more about ecology than behaviour. By the time I returned to Newcastle I had an offer. With no further discussion, Lack presumed that I would study guillemots on Skomer, since that was what I was going to do for John Parslow as soon as I graduated. With hindsight, I realise that Parslow and Lack had colluded -luckily for me.

The guillemotwasa fortuitous choice.Although Iwas interested in sperm competition I had no idea when I started my DPhil. that the guillemot, despite being socially monogamous, was sexually rather promiscuous. The observations I made were promising, but I soon realised that without a large number of individually marked birds in close proximity, guillemots would take me only so far in sperm competition. On moving to Sheffield in 1976 I started what would become a 10-year study of magpies to look at mate-guarding and extra-pair behaviour. But I was still in love with sea-birds, and I spent the next seven summers in various parts of the Canadian Arctic. Labrador, however, was the tipping point. The colonies there provided exactly the opportunity I needed to follow the behaviour of individually recognisable guillemots. As all the pieces started to fit together, I made the decision in the spring of 1983 that from then on sperm competition would be the main focus of my research.

Social behaviour was only part of the story. A true understanding of sperm competition also required a proper understanding of the mechanistic aspects of reproduction: how sperm were utilised, where and

Tim Birkhead and zebra finch. Photo: Francesca Birkhead.

when fertilisation occurred, and so on. Capitalising on avicultural skills acquired as a teenager, I made the zebra finch Taeniopygia guttata one of the two model species I would study (Birkhead 1996).

The second was a serendipitous choice - the fowl Gallusgallus. In the late 1980s I was invited to a meeting at the University of Stockholm's field station at Tovetorp in southern Sweden. During a tour of the facilities we were shown enclosures containing lynx Lynx lynx, moose Alces alces and other macho large mammals, all of which were being studied by rather macho research students. Suddenly a group of feral fowl (a primitive domestic fowl very similar to the red jungle fowl) scuttled past us and a male forced a copulation almost at our feet. Taken aback, I asked my host which of the various research students was studying these birds. Slightly incredulous, he said 'no one' - they were simply 'decoration'. I was intrigued, and a year or two later Tom Pizzari (see Chapter 10) was there as my PhD student studying their behaviour. I had mentioned to Tom that if he could persuade the cockerels to copulate with a stuffed female we might be able to obtain natural ejaculates, as I had done with zebra finches, and thereby gain new insights into both their copulation behaviour and the mechanics of sperm competition. It seems surprising that after decades of poultry research, no one knew how many sperm a male transferred during copulation. Despite his best efforts, Tom was unable to persuade the males to perform with his stuffed female. I went out to Sweden and one afternoon, as we watched the birds together, Tom was called away to the phone. In his absence I caught a live female (they were habituated and extremely docile) and, placing her feet between my fingers, crawled on my belly, with her rear end facing away from me, towards a cockerel. Slightly incredulous at his good fortune, the male mounted and inseminated the female. I let her go and tried another female. It worked again. I knew then that we were on the threshold of something exciting. Tom returned from his phone call, and I said to him, 'Watch this.' Once again the birds performed. Within a matter of hours we had devised a way of collecting ejaculates from the female, allowing us to measure ejaculate size and opening up a rich new avenue of research (Pizzari & Birkhead 2000, Pizzari et al. 2003).

What has guided my research? (1) First and foremost, a ceaseless intellectual curiosity about the natural world. The freedom I had as a youth to spend countless hours watching birds and other animals honed my field skills, fuelled my fascination for biology and gave me a strong sense of what I call biological intuition. That is, recognising what is biologically meaningful, what it is likely to work and what isn't. (2) Enthusiasm. I'm not sure where enthusiasm comes from, but my zeal was fostered and encouraged by my parents, and it has continued to provide the drive and tenacity that research requires. (3) Excellent teachers and wonderful colleagues. The Edward Grey Institute provided a particularly stimulating, challenging and instructive environment when I was a D.Phil student. Subsequently I have been extraordinarily fortunate to have had a succession of outstandingly able research students and other colleagues to keep me on my toes. (4) Open-mindedness. By this I mean reading and interacting widely (not just within behavioural ecology), and embracing broad horizons. There is no better way of generating new ideas than looking beyond the boundaries of one's own discipline (Birkhead 2008).

Finally, the best thing of all about being a behavioural ecologist is that one's enthusiasm for the natural world actually increases over time. The more we discover, the more we discover that there is still more to discover. Even after 40 years in the business, my passion for birds and for biology in general is even greater than when I started.


Birkhead, T. R. (1996) Mechanisms of sperm competition in birds. American Scientist, 84, 254-262. Birkhead, T. R. (2008) The Wisdom of Birds: an Illustrated

History of Ornithology. London: Bloomsbury. Birkhead, T. R., Johnson, S. D. & Nettleship, D. N. (1985) Extra-pair matings and mate guarding in the common murre Uria aalge. Animal Behaviour, 33,608-619. Pizzari, T. & Birkhead, T. R. (2000) Female fowl eject sperm of subdominant males. Nature, 405,787-789. Pizzari, T., Cornwallis, C. K., Lovlie, H., Jakobsson, S. & Birkhead, T. R. (2003) Sophisticated sperm allocation in male fowl. Nature, 426, 70-74.

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