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  • Post date: 5 months 4 days ago
    Citation for this post: BibTeX | RIS

    In in Nature in 1992, , Andreas Helbig, Gabriele Mohr and Ulrich Querner provided experimental evidence to show that central European blackcaps (Sylvia atricapilla) had evolved a new winter migration route, and established a new winter home over 1000 km away from their old one, in less than 30 years. Twenty-four years after the paper was published, I spoke to Peter Berthold about the making of this study and what we have learnt since then about the migratory behaviour of this species.

    (Interview conducted via Skype on 27th July 2016)

    Citation: Berthold, P., Helbig, A. J., Mohr, G., & Querner, U. (1992). Rapid microevolution of migratory behaviour in a wild bird species. Nature 360: 668-670.


    Hari Sridhar: At the time when you published this paper, in 1992, you had already done a lot of work on migration, especially on blackcaps. What got you interested in the work presented in this paper?

    Peter Berthold: We were really astonished by how rapidly changes in migratory behaviour can occur. When I was a student, I had learnt that, say, for changing a migratory direction or migration time by a week or so would take hundreds, if not thousands or tens of thousands, of years. And some people even doubted whether, after the Ice Age, any novel development of migration in Europe could have occurred. So of course, in the first instance, we couldn’t believe that within, let’s say a few decades, birds could change their migratory direction from a hitherto south-south-westerly-south-easterly direction to northwest, to England. This was baffling for all of us. And also for geneticists to whom I had spoken about it. This was the main reason to publish it.


    HS: This paper has four authors. Could you tell us how this group came together and what each person brought to this study?

    PB: Andreas Helbig was a PhD student, Ulrich Querner, at that time, was one of my main technical assistants, and Gabriele Mohr was also a technical assistant.


    HS: Was Andreas Helbig your PhD student?

    PB: Oh yes, he was in my lab and also in the laboratory of . You may have heard about the name Wiltschko. They are a scientist couple living in Frankfurt who have been the leading authorities on orientation research for a long time in Germany. Wolfgang Wiltschko discovered magnetic orientation in birds.


    HS: Did Helbig continue in a career in research after his PhD?

    PB: Yes, for a number of years, but then, unfortunately, he died of cancer. It was very sad.


    HS: I’m sorry to hear that.

    HS: In your paper you say you transported these birds back from Britain to Germany to do the experiments. Can you tell us a little about how you actually did this?

    PB: This is as we have always done this – they were trapped with mist-nets and then put in small cages. There is a critical time in the beginning, especially on the first day, when you need to make sure that the birds will take food in the cage because otherwise they will die. Therefore, we have developed very specific methods to do this. The rest is very easy - to take them into a car, or from other countries, even by plane. This is something we had developed in our institute in a unique way. In this respect, we have been the world champions.


    HS: How long did it take to drive from Britain to Germany?

    PB: Less than a day.


    HS: Did Andreas Helbig do most of the experiments?

    PB: The experiments were run in a large group of people, including many technical assistants. The scientific investigations we did together, step by step. I would say it was split about 50-50.


    HS: I want to find out a little more about the sites in Britain where you trapped blackcaps. You acknowledge a couple of agencies for permissions. At that time, was it difficult to get permits to move birds from one country to another?

    PB: [Laughs] Not on principle. But of course, you know how it is with Britain, you have belonged to Britain for a long time. In most countries it was very easy to get permissions to take birds – France, Spain, Portugal etc. But the British, they say – Oh, these are our birds, and we normally don’t give permits.  So we told them – Listen, these birds that we would like to take from Britain are birds from Europe. They come only to winter with you. They are very bad continental intruders, and you should be happy about every bird that’s leaving England a little bit earlier than normal. You should be grateful to us for taking these food robbers from the British islands back to the continent. Then they said – Oh yes, of course, you will certainly have the permits to take these birds away.


    HS: How did you pick the site in England – near – to trap the blackcaps for this study?

    PB: This was an area in southern Britain, and we had two reasons to trap here. First, this was an area which had one of the highest densities of wintering birds from continental Europe. And second, this is an area with a lot of traps in the dunes, where it’s easy to post mist nets and drive the birds. The British people are very critical about mist-netting, and don’t allow it in their house gardens. In mid-England we have faced a lot of difficulties. But in these coastal areas it was very easy. So let’s say we had chosen the area for good practical reasons.


    HS: In the paper, you say you used a “modified Emlen technique” for the migration direction experiments. Can you tell us what the modification you made was?

    PB: You know, and inkpads on the ground. The birds would sit on ink pads and when they try to leave the cage they produced these footprints on a white paper. In our technique, developed by Wiltschko and Helbig, we used rubber paper on which the feet, and especially the nails or claws, produce small scratches. These scratches are much more easily counted and investigated. For analysing all these scratches we have developed a specific computer program, which would take all the papers with the scratches and calculate the mean value of the direction and other necessary statistical values.


    HS: Is migration still studied with similar apparatus?

    PB: I think it’s rarely used now. The Wiltschko group continues to fit the data by eye. Now, in Germany, we have no other institute that’s really doing orientation research with songbirds. Only with larger species. In America they continue to use Emlen’s method.


    HS: Have you gone back to the site in UK where you trapped birds, since you did this study? Do you know what the status of the site is?

    PB: The site is the same as it was then. It is a protected area. But, of course, with climate warming, there will be changes!


    HS: Have the blackcap numbers changed in this site?

    PB: They have increased, and are still increasing. This development, started during my time there and is still going on. Now we have blackcaps wintering not only in Great Britain, Scotland and Ireland but also in southern Norway up to Finland. So the whole north is now a large, more or less closed, wintering area of blackcaps coming from continental Europe.


    HS: Has this increase been documented systematically?

    PB: It has been studied systematically by the British people. It’s quite easy because all British blackcaps are leave the breeding area during winter, and so the blackcaps you observe wintering in England are all from the continent. And the bird counts in Britain, as you know, are, by far, the best in the world. They count every individual.


    HS: Do the outdoors aviaries that you used during these experiments still exist? Are they still used for experiments today?

    PB:  Yes, they exist, but they have been changed. They have been enlarged. I’m retired for about 10 years now, and my successors no longer work with blackcaps. They work with blackbirds – Turdus merula - and the blackbird is, of course, a larger bird than the blackcap, and so the aviaries have been enlarged. What we used to called blackcap city is now blackbird city!


    HS: Who did most of the writing for this paper and how long did it take?

    PB: It was written by Helbig and me. Writing itself was very easy. It was done in three days or so. What took time was running the experiments - doing the orientation experiments took time, and the statistics to some extent. Once you are at the stage where you can start writing, it is very easy after that.


    HS: Were the other two authors also involved in the writing?

    PB: No, they were only involved in running the experiment and compiling the raw data.


    HS: How did the writing actually happen – would you and Helbig sit together and work, or would you share drafts on a computer?

    PB: At that time we didn’t use the computer. Till today, I do all my writing, even of books, by first hand-writing, then by dictating and getting it typed into a computer. Still in the very old fashion way.


    HS: So you would sit and write it together?

    PB: No, we would each sit each somewhere in a corner and write, and then come together and exchange what we have written. It doesn’t really work to sit at a table and do it in a combined way. That way you talk about everything but science!


    HS: How were the figures in this paper drawn?

    PB: They were hand drawn, just on a sheet of paper. The orientation figures, as I already mentioned, were made by a computer from the very beginning. The computer did all the analysing and also the printing.


    HS: In the paper you thank C. Mead, G. Pudney and T. Parsons. Could you tell us who these people were and how they helped?

    PB: They were all people from England. Mead was the head of the ringing office of the British Trust for Ornithology (BTO) in England. He was a good friend of mine and we asked him to help us get the permission to trap. The other two were ringers of the BTO, who helped us trap birds in the field.


    HS: You also thank someone by the name of H. Dingle for comments.

    PB: Yes, . He is an American. He was and still is working in the University of Davis. Hugh Dingle is a very famous investigator on birds and insects. He has written an interesting book on bird migration, as I have done, but his main focus was on partial migration. I had invited him to come to Germany, to stay here in my institute, as a Humboldt Research Prize winner, for half a year. This was a very fruitful time during which we discussed all aspects of the genetics of bird migration. And he also gave a lot of input into this specific paper.


    HS: Did this paper have a relatively smooth ride through peer-review?

    PB: Oh yes. It was very easy. We got a few very small comments. The reviewers were really enthusiastic about the paper, and so it ran through.


    HS: And Nature was the first place you submitted this to?

    PB: Oh yes, of course.


    HS: How was this paper received at the time it was published? Did it get a lot of attention?

    PB: Oh yes. All over the world. And, of course, also in the Max Planck Society. In the meantime we have published a number of papers that are very similar in their content. But this was something like a small revolution, because of the idea of how rapid and how quickly and how efficiently micro-evolution, and therefore evolution as a whole, can work in the living world.


    HS: What impact did this paper have on your future research itself? Did it open up new lines of investigation?

    PB: This was a milestone in our own research. Following this, we thought about many aspects that could be followed up and that led to a whole series. It finally led to a totally novel theory on avian migration. Just in about 5-6 generations. Then the discussions with Hugh Dingle really showed us that partial migration is, in fact, a common habit in all kinds of animals and even plants. From the oldest pre-Cambrian bacteria up to humans, you have partial migration. Wherever you look around partial migration is there. This is probably a habit as common as, let’s say, circadian rhythmicity in plants and animals. Then we looked carefully into the literature on the world’s bird species – now about 10,000 – . And even among the remaining, some proportion might be migration. Take the house sparrow.  As you know, house sparrows are normally resident, but if you look carefully at them – like it has been done by in England - about 1-2% of the birds are migratory. It’s a small amount, but still. So even one of the most typically resident bird species all over the world is a partial migrant. Based on all this evidence we developed the theory that partial migration is a basic equipment of all living avian species. Therefore it would be very easy for birds to adapt to all kinds of environmental changes, whether ice ages or climate warming, because even a species like the house sparrow could easily develop in 10-20-50-100 years a fully migratory population, if conditions at home become unfavourable. Or the other way around – a population of barn swallows, now a migrant in Europe, could develop, in about 40 years or 25 generations, a totally resident population, something that I think we will have in the next 50 years or so. All this was initiated by the paper in Nature at that time.


    HS: Its now 24 years since this paper was published. Would you say that the major conclusions from this paper still hold true, more-or-less?

    PB: [Laughs] No, it doesn’t only hold true; it has become, let’s say, a common sense. At that time we wrote that this maybe a unique rapid micro-evolutionary process that we have observed. Since then we have come to learn from many other papers, many other plants and animals, that this is not an exception. This is normal. But it was absolutely overlooked before we did this experiment. You may have heard about from America, from the Princeton University. . They were astonished when, once, after a big drought, a specific population of ground finches went almost extinct, but after a while started to not only survive but also to increase the population again. This was due to the fact that they had developed, in a very short time, extremely strong beaks with which they could open the only seeds that could be harvested in the extreme drought. And when the normal climatic conditions came back to the Galapagos the size of the bill was again reduced to normal size. All this happened within about 10 generations. We have so many more examples – e.g. snakes that lay one more egg in a clutch and so on.  And all this can happen within a few generations, in about 10 years or so. So this is now a general biological aspect. Therefore, I would say, the paper opened an area of understanding of how rapid and effective evolution can work everywhere in the world.


    HS: If you were to redo this experiment today, would you change anything, given the developments in technology, theory and statistical techniques?

    PB: No, certainly not. The only way to show this was to do some breeding and selection experiments. That was the only way. Today, in parallel, we would also look in detail for the genetic structure of the individual birds, i.e. for the genes itself. This is, of course, very very difficult way in birds, but we have managed to do this. That’s something we would do in addition, but the rest would be done as before. There’s no other way around.


    HS: And you would still use the modified Emlen funnel?

    PB: Oh yes. That is the best way you can do it. There’s nothing better in the world.


    HS: In the paper you flagged a few topics about which not much was known, and which you felt needed to be researched further. One of these is the genetic basis of this migratory evolution. Do we know more about that now?

    PB: No, this is still not possible. Because you see, while you can easily find differences in the genomes of different species, between populations you find only very very slight differences. You have no idea to what they are really related. So it will be some more decades before that will be possible.


    HS: You say “Overall mean directions suggest a breeding origin between Belgium and central Germany”. Do we now know, with more certainty, where these birds wintering in Britain come from?

    PB: Oh yeah, we know now. There have been many more ringing recoveries, and many other investigations, based on which we can say this is an area that roughly goes from the south, from Switzerland and Austria, up to Vienna in east Austria, and then up to about almost the whole Germany, up to the area of Hamburg and east Germany. This is the big patch from where the birds that nowadays migrate to England are coming.


    HS: Do we also know more about why this change in migratory direction happened?

    PB: Yes.  We must distinguish between the mechanism that has started this development, which was of course chance, and what maintains it. There is a lot of genetic variation and, by chance, some birds extended the westerly migratory direction to this slightly northern direction, and so by chance they reached England. If England would not have existed they would have gone into the Atlantic Ocean and the story would have ended. But fortunately there was England. And then the birds that entered England had, let’s say, a funny experience – a wonderful land, a mild winter, not so many birds in the winter, in comparison to Spain or France where so many birds from northern Europe were wintering. It was a paradise and therefore, of course, there was a strong selection pressure to increase the number of birds coming there. Now this work has been investigated in further detail. We had already, in our paper in Nature, the idea that this direction change could be accelerated by, so called, assortative mating. We knew already that birds wintering in Britain migrate back to the continent relatively earlier in the breeding season. Also the distance is relatively short. We have followed this up in more detail. We have looked in continental Europe for the very first breeding pairs of blackcaps. From these birds we have taken small amount from the claws, because the claws are growing in the wintering area, and in these claws must be stable isotopes that show exactly where the birds have been wintering. By this method we have found that the very first broods in central Europe are, more than expected, from parents that have both wintered in England. This means that, through assortative mating, there is an acceleration of the new migratory direction development. . The first author is Stuart Bearhop. In this we showed that there is a high selective advantage. The birds that winter in Britain come relatively early to Germany, choose the best habitats, mate assortatively, and have the possibility of having more than one brood. This is, I think, the main selection force behind the rapid development of these new migratory habits.


    HS: Towards the end of the paper you say “Year-round residency has not yet evolved in British breeding blackcaps, but this may be only a matter of time”. Are there any indications that this is happening now?

    PB: Oh yes. This will, of course, come in, sooner or later, due to climate warming. Experimentally, we have already shown that this can happen very easily. So when a population is migrating shorter and shorter distances, due to climate warming, the number of resident individuals automatically increases. We have shown this in a very nice experiment. We took birds from an exclusively migratory population of blackcaps, in this case from south of Germany, and from these, chose the 30% with the lowest amount of migratory activity, i.e. the 30% with the shortest migratory distance. These birds we have selected for lower and lower amounts of migratory activity. In this way, after 4 or 5 years, we had the first 10% of non-migratory individuals from a hitherto fully migratory population. And from this we could calculate how long it would take for a totally migratory population, by directed selection, to convert to a non-migratory population. We found that would be about 40 years or 25 generations. And this is something that will happen in many many bird species during the next 100 years or so. You can read more about this in two places – one is my bird migration book - the English version that has been published by Oxford University Press. This was in 2003.


    HS: Do you continue to work on this topic even today?

    PB: No, this is absolutely impossible. I have given this up on retirement, because for this you really need a large institute and a large group of people. Now, I’m totally engaged in conservation issues and totally different things.


    HS: Have you ever read this paper after it was published?

    PB: I think I have read it a few times, when I was writing reviews on bird migration or when I had to write a new edition of - in German, it’s now in its 7th edition. Then, of course I go back into original papers. Sometimes, I also go back to it to see the wordings I used to deal with sophisticated concepts or ideas.


    HS: When you compare this paper to those you write today do you notice any striking differences?

    PB: No, the style has been about the same. I have been writing every week so there hasn’t been much change. The brain is still working to some extent.


    HS: This paper has been cited over 300 times. Would you know what it is mostly cited for?

    PB: No, I never have looked for citation index. This has never been, for me, of any interest. I was convinced that this was an important paper and that, sooner or later, it will be noticed. Citation indexes are very modern instruments and in many cases absolutely useless. We have had endless discussion in the Max Planck society about how to handle this. This is of no interest for me.


    HS: Would you count this as one of your favourites, among all the papers you have written?

    PB: Oh yes, absolutely. This is certainly one of the five best papers we have made.


    HS: What would you say to a student who is about to read this paper today? What should he or she take away from this paper?

    PB: I think the most important thing is that if you have a good idea, and if in coming to a solution you have a lot of difficulties, like we had  - to get the birds from England, to take them over, to run long-term experiments and so on – do not give up and keep going. Because in the end you will either be happy to have excellent results or will anyway face many other problems but without any good results. So I think you should not hesitate to choose the hard way.


  • Post date: 5 months 1 week ago
    Citation for this post: BibTeX | RIS

    In 1998, , , and published in Science providing evidence to suggest that killer whales were behind the sudden declines in sea otter populations in western Alaska in the 1990s. Estes and colleagues also showed in this paper that the otter decline had, in turn, led to an increase in sea urchin numbers and consequent deforestation of kelp forests. Eighteen years after the paper was published, I spoke to James Estes about the observations that motivated this study and what we have learnt since about the killer whale’s role in this system.

    (Interview conducted via Skype on 22nd July 2016)

    Citation: Estes, J. A., Tinker, M. T., Williams, T. M., & Doak, D. F. (1998). Killer whale predation on sea otters linking oceanic and nearshore ecosystems. Science 282: 473-476.


    Hari Sridhar: Would you consider this paper a turning point in your career? The reason I ask is because this was your first paper on a whale species, and subsequent to this you have done a few more. Would you say this paper had a strong impact on your research trajectory?

    JE: These discoveries certainly influenced my career trajectory. It wasn’t so much just the paper, but also the information, observations and research that lead up to the writing of that paper. This may be a matter of interest to you.  Initially, I was reluctant to even submit the paper. And that was because, in contrast with everything I had done in my career prior to that time - I actually started field research in that system in 1970 and this paper was published almost thirty years later - which was forward-looking and question-oriented, this killer whale stuff was very retrospective. In other words, there was absolutely no expectation of these sort of things happening. It was the accumulation of these unexpected observations that led to the retrospective analysis, which was an effort to try to sort through what we thought was going on, what the evidence was, and so on and so forth. So I felt very uncomfortable about it, and it was only because of, mostly, the reaction of colleagues that it was an interesting story and their urging that it should be submitted, that we finally went forward with it.


    HS: What were the observations that led to this paper? When did you first suspect that killer whales might be responsible for the decline of sea otters?

    JE: Well, actually, killer whales weren’t part of my view of what was going on, initially. It all started in the early 1990s when I began a project to study the life history and behaviour of sea otters at . Sea otters are apex predators, the population at Amchitka Island was thought to be at carrying capacity, and the broader goal of our study was to describe and understand the life-history patterns and behaviour of an apex carnivore at carrying capacity.  That is why we went back out to Amchitka Island at that time. We had quite a large number of hypotheses about what we should see, and we were trying to test them rigorously by contrasting data from Amchitka Island, where otters were thought to be at or around carrying capacity - they had been in my mind for decades - with a nearby island – - where they had recently become recolonized. We wanted to contrast body condition and foraging behaviour and reproductive success and mortality and so on, between those two circumstances. When we did the work at Amchitka, nothing fell into place. I mean, none of the expectations were met. So, for instance, I had expected to find a lot of dead animals on the beach. I didn’t find any. I expected to find animals that were in relatively poor body condition, because of competition for food in a population around carrying capacity. The data simply didn’t show that. I expected the otters to spend a lot of time feeding. They didn’t, they spent much less time feeding than I thought they should. And all of these other things. So when we finished the study at Amchitka - I think it was around 2004-2005 - I was completely befuddled. I just did not understand what was going on. But very fortuitously, we had the opportunity to continue the work at, which was a place that was fairly similar to Amchitka, in terms of the history and status of its sea otter population.  It was during the time of that work at Adak that we started to see that the otter population was not stable at or around carrying capacity but in fact was declining and to think that killer whales might be an important part of it.  The time series of population surveys had progressed long enough by about 1995-96 that there was no question about the decline. But we didn’t understand why. And then, over the course of those several years, we had seen a lot of killer whales and several attacks on otters. That was very much in contrast with anything we had ever seen up until the early 1990s. To that point we had rarely seen killer whales, and never seen them attack sea otters. And so those observations, altogether, were what led to the suspicion –an emerging hypothesis - that killer whale predation was driving the otter population downward.


    HS: How did the four authors who wrote this paper come together? What did each bring to the paper?

    JE: There was myself, Tim Tinker, Terrie Williams and Dan Doak. Tim Tinker was working for me as a field technician at the time. He spent some time at Amchitka and then ran the field program at Adak. Tim was in the field at Adak throughout the year. In addition, we had volunteers who were working under his direction. I was out there mostly during the summers, because I was teaching and so on at other times, but Tim was in the field all the time. That was his role. Then, as we became more interested in why the otter population was declining and started analysing the data, we felt that we needed two other areas of expertise. One was somebody who could do demographic modelling, and so we invited Dan Doak to join us. Dan was a faculty member at UC Santa Cruz at the time. And then we felt we needed somebody who knew something about marine mammal energetics, to understand how much killer whales eat and assimilate and that sort of thing. Energetics became an important part of our conceptualisation of the modelling we wanted to do. That was Terrie Williams’ job. That’s how the four of us came together on the paper.



    HS: Did the four of you ever meet as a group, or was it all done remotely over phone and email?

    JE: No, we often met as a group because we were all at Santa Cruz. By the time we wrote that paper, Tim Tinker had come back to Santa Cruz and had joined my lab as a graduate student. And both Doak and Williams were faculty members at Santa Cruz, so all four of us met and talked frequently.


    HS: Do you remember how long the writing took?

    JE: It is hard to say because the paper took form though various iterations. It didn’t take very long to write the initial draft, probably a couple of days, once we had our ideas, analyses, and figures together. But then we went through quite a large number of iterations, which probably took three or four additional months. When the paper was originally submitted to Science- which was probably in 1997, I am not sure exactly - it was rejected without review. At that time, I had intended to just let it go, but another colleague of mine at Santa Cruz by the name of , who is a behavioural ecologist, changed my mind. I happened to give a lecture to his class about this work. Bruce thought it was interesting and asked me where it would be submitted at the end of my lecture. I told him what had happened with Science and he urged me to challenge the decision, because he felt it was very important work. I had him look at the paper, he made a couple of suggestions, and I resubmitted the paper with a letter requesting that they re-evaluate it. And they reviewed and accepted it.


    HS: Did you do most of the writing for this paper?

    JE: I did most of the writing, Tim and I did much of the analysis, Dan Doak did the modelling work that involved figuring out how many mortality events occurred and that sort of thing and Terrie did a lot of the energetics research. She determined the calorific value of otters, the metabolic and assimilation rates of killer whales, and that sort of thing. So yeah, I did most of the initial writing, but the others did a lot of follow up and provided important details.


    HS: At the time it was published, did it attract a lot of attention? Were the findings considered controversial then?

    JE: No, I don’t think the findings were controversial, at least no one challenged any of the results in print at that time. I know that there were people who were skeptical, based on written exchanges and verbal discussions I had with them. And I thought that was fine, because the paper was a sweeping interpretation, and certainly was not an experimental study. Yes, there was a tremendous amount of media interest in the paper. I spent weeks talking on the phone to people in the media about the paper.


    HS: What do you think was the main reason for the interest – was it the system itself or was it the killer whales?

    JE: I think the main reason for media interest was because of the players--killer whales and sea otters. It wasn’t so much the conceptual part of it that interested the media. I think it was the idea that these very charismatic species were interacting with one another in seemingly such a bizarre manner. But there also was the perception of significant ecological impact. People understood that not only were killer whales eating sea otters but that this was having a big impact on the ecosystem. So I think those things together—the players and their interactions--were probably what attracted so much interest and attention. The question of how we made the discovery came up frequently in talking to journalists and other people about the work.


    HS: Today, 18 years after the paper was published, would you say the main conclusions still hold true, more-or-less?

    JE: In my opinion yes. I think everything that we have done and seen subsequently has supported the initial interpretation. I would say there have been no qualitatively important breakthroughs, or new information, one way or the other. But there has been some quibbling. There was - maybe three or four or five years ago now - in Mammal Review that criticized our work. We were never invited to respond to it, but we submitted a rejoinder response anyway, which was not accepted. That was a dark corner. I don’t know if you have seen that paper, but you should read it. It’s by Katie Kuker and .


    HS: In your paper you draw a picture of the scenario at that time and how it might have come up. Then you say “Parts of this scenario are well documented, others are more speculative and still others have yet to be evaluated”. Do we have a more complete picture now?

    JE: Somewhat. The conclusion that the otters declined is unequivocal. I think the conclusion that there was a radical phase-shift in the kelp forest system that was caused by the loss of the otters also is unequivocal. We’ve seen this over and over in different settings, and it happened with the loss of the otters out there. We had very good documentation of the kelp forest ecosystem and those data are summarized in our Science paper. I think the conclusion that it was caused by killer whales will always be somewhat uncertain, just because of the nature of the data. I think the evidence is quite strong but certainly not definitive. At the time, and if you read the paper carefully, you will see that we speculated that the decline of Stellar sea lions during the 1980s was what prompted the killer whales to start feeding on sea otters. And I had imagined at that time, mostly because this was the conventional wisdom, that the decline in Stellar sea lions was a consequence of some food related problem, either because of an oceanic regime shift or because of fisheries or some combination of those two things. I now think that interpretation was wrong. I didn’t realise it at the time, but subsequent evidence for food limitation in the sea lions is counter-indicated. The weight of evidence suggests that, in fact, the sea lions had lots of food. And so I believe that the sea lion decline and the otter decline are linked, and are probably linked in the way we had initially imagined, which is that the sea lion decline led to the sea otter decline. But the cause of the sea lion decline I now see as being fundamentally different from what I had thought at that time. . I didn’t recognise that at the time.


    HS: Have these areas changed since you worked there for the study? What’s happened to the otter population?

    JE:  Nothing much. At the time that paper was published, the sea otter populations had declined by about an order of magnitude. They continued to decline, and otters on some of the smaller islands in the Aleutian became extinct. The present densities are holding more or less constant at very low levels overall. There is no obvious trend in any of the survey data over the last decade or so. We now have fairly long time-series of abundance of counts from surveys on different islands from the early 1990s right up to the present. What all of those data suggest is that the population has declined by 95-98 % in most places, or at least to 95-98% below carrying capacity, and that it has remained relatively constant to the present. I wasn’t out there this summer, but I was there the year before, and then the numbers and such were as I have described.


    HS: Do you continue to do research in these areas?

    JE: Yes, I continue to do some work out there. Mostly it’s monitoring work. I am 70 now, I had an ear injury, and so I’m not diving any more. And a lot of the research requires diving. My students, who now work in different places, are continuing to do research out there. We are continuing to monitor otter populations. There are numerous sites where we are monitoring both kelp forests and the otters, so we continue to do that as opportunity and funding permit. I will be going back again next summer to help with another project. But most of the work that I have been doing since the early 2000s has focussed on related issues. Not so much on the killer whale business, but on different parts of the kelp forest ecosystem. We are currently finishing up a 3 year study of the system’s historical ecology, as it’s recorded in the growth of long-lived encrusting coralline algae. We’ve been looking at things like ocean acidification and how that interacts with kelp, and issues of that sort.


    HS: In the paper you talk about Clam Lagoon as being “uniquely inaccessible to killer whales”. Why is that?

    JE: Clam Lagoon is a place that was created by a receding glacier. The moraine formed the barrier between the lagoon and the outer ocean, where the killer whales are. The water between Clam Lagoon and the open sea breached at some point in the past, so there’s a narrow, shallow connection between the outer ocean and Clam Lagoon. Clam Lagoon is quite large, about two miles long by a mile wide, and it supports a population of roughly a hundred otters, and that number of animals has remained more or less constant from the time we began working on Adak in the mid-1990s. So Clam Lagoon was created fortuitously by this geological event, and the connection between Clam Lagoon and the open sea is too shallow for killer whales. They just don’t go in there.


    HS: In one of the notes to the paper you say that your research team spent 21,677 person hours in field. That is a lot of field time! Could you give us a sense of over what period this was, and how many people it involved?

    JE: Well, I had been working in the Aleutians for more than 25 years at the time. And we were in the field every day from morning till evening. I usually worked with a team of four people during the later years. Early on, during the 70s and up to the early 80s, it was usually just two of us, and then after that it was commonly four. So, there were a lot of people, over a lot of days, over a lot of years, and when you sum it all up, the number of person hours in the field becomes  very large.


    HS: In the Acknowledgements, you talk “about a contract from the U.S Navy”. What was that for?

    JE: I had mentioned to you before that I worked at Amchitka in the early 90s, when we were looking at the life history and behaviour of otters. That work was funded by the US National Science Foundation. After I left Amchitka, the Navy supported a follow up study at Adak. What happened actually was that, as I was leaving Amchitka, as we were wrapping up the study at Amchitka in 1993 or 94, I happened to be talking with Dan Boone, who was the manager of the Aleutian Islands Unit of the Alaska Maritime National Wildlife Refuge. He approached me and said the military – both the Navy and the US Air Force - were interested in having work done on sea otters at their respective military bases. Adak was a naval base and Shemya Island, where we worked some years later, was an Air Force base. There was a military programme, called the , which was for doing wildlife and ecological research on US military bases. Some of that Legacy money had gone to those particular sites and the Aleutians Refuge was asked to advise the military on what to do. That’s how I got involved with it.

    HS: Were the people who you thank for field assistance – C. Dominick, B. Konar, J. Meehan, K. Miles and J. Stewart –all students?

    JE: C. Dominick was a student helper who worked with us at Adak. was one of my graduate students, who at the time this work was done was just finishing her dissertation research at Shemya Island. Brenda helped me with the diving work. J. Meehan was an employee of the Fish and Wildlife Service, who helped us at Adak. K. Miles was an employee of the US Geological Survey, also my employer at the time, and he came out to the Aleutians to help me with diving on various occasions. is now Tim Tinker’s spouse, but she was his partner at the time, and they worked together during the 1995-95 period on Adak. She was also a trained field biologist and helped Tim with the fieldwork.

    HS: Could you also tell us about the people you thank for comments on the manuscript?

    JE: was a post-doc. at Santa Cruz at the time. He is now, and for a long time has been, a faculty member at Lewis & Clark College in Portland, Oregon. is a fellow faculty member at the University of California (UC), Santa Cruz. was one of my graduate students at the time. He worked with us in the Aleutians. He is currently an employee of the National Oceanic and Atmospheric Administration (NOAA) and works at the Santa Cruz Fisheries lab. is another fellow faculty member, a terrestrial plant ecologist from UC, Santa Cruz. Bruce Lyon is also a fellow faculty member at UC Santa Cruz. Lyon is the person who I referred to earlier, whose class I was speaking to, who urged me to resubmit the paper to Science. is an ecologist I met decades ago, when he was an undergraduate student at the UC Santa Cruz. We’ve remained close over the years. He is a research ecologist, and has been for a long time, with the Cary Institute for Ecosystem Studies in New York. is a professor at UC, Berkeley. is a professor at the University of Alaska. Springer and I, subsequently, did some work together and published, which you may have read, that linked all of this stuff to whaling.

    HS: Towards the end of your paper you talk about intersystem linkages becoming increasing well-known at that time. Subsequent to your paper, do you get the sense that people went out and looked for other such linkages?

    JE: It’s hard to know. That was one of the big messages, or one of the revelations, that came to my mind in thinking about what it all meant. I would like to think that our paper impacted people in that way. The results certainly influenced my thinking. It’s hard to know how other people have thought about these things. A few years before our paper was published, and several others published an on subsidized ecosystems. That paper explained how ecosystems are linked together, and most of the case studied that Polis talked about were connections between land and sea - nutrient subsidies from the ocean to land and so on and so forth. The Polis paper motivated me to start thinking about these issues. Before he published that paper, I think most people imagined that adjacent ecosystems function into themselves, more or less separately from one another. The intriguing feature of our study was the idea that linkages between ecosystems resulted not only from material and energy flux, but from the movement of individuals and species, and that even relatively rare things like killer whales could potentially have big effects. I don’t know how much that idea has trickled down to other people. I think it probably has had some impact on the way people think about how nature works.

    HS: What would you say to a student who is about to read this paper today? What should he or she take away from this paper 18 years after it was published?

    JE: Well, let me think a little bit about that. I think maybe three or four things. One is the serendipitous nature of the way the science was done. That’s really the theme of . When you read that you will see that that’s really what I’m writing about. This was not a question-driven or hypothesis=driven study. It was a retrospective study and very much based on, what I call, serendipitous events. Things that happened that we were perhaps lucky to see. The second point I would make is more theoretical and has to do with food web structure and dynamics--the idea that effective food chain length has strong impacts on the nature of plant-herbivore interactions. So this is really a follow-on from the ideas of Stephen Fretwell- that even-numbered food chains cause strong plant-herbivore interactions and odd-numbered effective food chains cause weak plant-herbivore interactions. Fretwell published two papers - and the other was in 1987. The . That was where he really proposed his theory. What we have in this particular study is documentation of the dynamics of plant-herbivore interactions in a food chain that is effectively two trophic levels - that’s just the urchin and kelp - three trophic levels when otters are added in, and four trophic levels when the killer whales become part of it. So our paper supports Fretwell’s hypothesis. Another important message is that what one discovers about nature may not be at all what one was expecting to see and learn. And I don’t know how strongly that comes through, but you know it took us several years to open our minds to the possibility that these things were going on, even though the evidence was there earlier that there were major changes happening. My belief system about the way that system was put together, and the fact that I thought the sea otter population was at carrying capacity, really prevented me from seeing the truth till later. I don’t know if that comes through from the paper. It definitely is a point of emphasis in my book. Finally, the idea that large predators can strongly influence ecosystem structure and dynamics. Those are the main points.


    HS: In the last sentence of the paper you say “These points emphasize the potential significance of large-scale ecological events and the consequent need for large-scale approaches in ecological research”. Could you tell us what exactly you meant by large-scale approaches?

    JE: Well, what I mean is this. I think a lot of marine ecology and coastal marine ecology especially has been very experimental, necessarily done at very small spatial scales. By small spatial scales I mean at the level of metres to tens of metres to hundreds of square metres, in some cases. Those are the sizes of the experimental units. The point I think was that, studies that are done at that scale, that are done in order to achieve experimental rigor - through manipulation and replication and so on - are necessarily going to be constrained to species whose behaviour,  life histories and spatial ecologies occur at those small scales. The time scales over which these experiments are done is also usually fairly short—usually no more than a few years. And the point I was attempting to make was that we have seen at least the hints of processes in this system that occur at much larger spatial and temporal scales. So the effect of otters was seen by comparing islands with and without otters. We simply can’t see that effect by looking at one particular island. It requires looking at islands that are separated by often times hundreds of kilometres to see that effect. And the impact of killer whales occurred at an even larger scale. It occurred at the scale of an entire ocean basin, or at least part of an entire ocean basin. So I was arguing that we need to be looking at patterns of variation in nature that occur over these very large scales to see these kinds of processes. I’m still not at all sure that people get this. Does that make sense to you? I mean, did that come across?

    HS: Yes, it does.


    HS: Would you count this paper as one of your favourites, among all the papers you have published?

    JE: Yeah, it’s one of them certainly. It was fun to write, I think it was an important paper, and it generated a lot of interest and attention. Is it my very favourite? I don’t know. , which was on the sea otter kelp trophic cascade, is to me, personally, the most important paper that I ever wrote. I’ve written a couple of other papers that I would say were comparable. I’ve written papers that I think were good papers, and I think this was a good paper given the questions and the nature of the evidence. But from the perspective of an experimental ecologist it was probably not a good paper. It’s not experimental ecology. But I liked it because I felt like we were able to make a reasonably compelling argument for the cause of this amazing pattern that we saw, and I feel good about both the philosophical perspective and the intellectual infrastructure that went into disentangling all this stuff. So yes, in that sense it was great fun.


  • Post date: 5 months 2 weeks ago
    Citation for this post: BibTeX | RIS

    This post was contributed by Christina Birnbaum, a postdoc at Murdoch University, Western Australia. Find out more about what she does by visiting


    The , along with local hosts the  celebrated the  11-15 September 2016 in Perth, Western Australia. Over three days, the delegates presented and discussed topics on herbicide resistance, existing and emerging agricultural and environmental weeds, biological control of weeds, new technologies and modeling to manage weeds. 

    Professor from the Australian Herbicide Resistance Initiative based at the University of Western Australia gave a powerful plenary and overview on sustainable technologies and agronomy to produce more crop with less weed management. Key messages from his talk were that new herbicide discovery is lagging behind; weeds are still the greatest biotic challenge to producing more food in Australia and avoiding weed resistance evolution can be achieved with diversifying control technologies. According to Stephen Powles it is estimated that 222080 new people are being born every day around the world, making the issue of food security more and more critical to address.

    I really enjoyed the inspiring keynote address by Susan Bower Breaking Bad – 10 Years into a projected 30 year weed eradication program on World Heritage Listed Lord Howe Island about weed management success stories from the Lord Howe Island in Australia. from the University of Adelaide presented his PhD work results on the negative effects of native Australian , an obligate parasitic genus of vines in the family Lauraceae, on the invasive shrubs scotch broom () and gorse (). These results are encouraging - showing that native vines may be in the future used as native bio-control agents to manage some environmental weeds.

    from the Department of Agriculture and Food, Western Australia run a workshop on invasive Cactii in Australia, which are an emerging ecological pest. from the New South Wales Office of Environment and Heritage presented new “technologies” for weed eradication, i.e. using detection dogs. The delegates got a firsthand demonstration of Sally the detector dog in action looking for hawkweed ().

    As part of the conference, I was invited to organise and Chair a session on invasive acacias – Wattle we do about invasive Acacias? This was my first experience in organising a session for the conference and was indeed a very enjoyable one! from the University of Coimbra kicked off the session by giving an international perspective on impacts and biocontrol options for Australian native species Acacia longifolia which is a significant environmental weed in Portugal.  from the University of Canberra then summarised the current state of knowledge on weedy acacias and the role of symbiotic associations with nitrogen fixing bacteria in their invasion success. from Federation University discussed what makes native Acacia longifolia subsp. longifolia a successful invader in south-eastern Australia.

    I was pleased to see so many people tweeting during the conference using the . Even now, preparing this blog post, re-reading some of the tweets helped me to remember the highlights of the conference. The three most prolific tweeters received recognition from the organizers, something that other conference organizers should follow, I think.

    The only thing I missed at the conference was an event targeted for next generation weed ecologists and ECRs (early career researchers). It would have been great to have a function just for ECRs to make the most of the conference time. Maybe this is something that could be included in the next Australasian Weeds Conference in two years in Sydney. 

    As an ECR, it was great to be involved in organizing the 20th Australasian Weeds Conference and running my own session. It inevitably gives an ECR better exposure and makes networking that little bit easier. Or if you are like me and just love organising events, then that is a reward in itself when things work out and run well!

    Overall, it was refreshing to participate in a conference that has such a strong applied focus.  It was also great to witness that some of the invasion ecology science is being implemented in day-to-day management actions to control the weeds in Australia.

     If you would like to find more about the conference, visit CAWS website where you can view and download all the

  • Post date: 5 months 2 weeks ago
    Citation for this post: BibTeX | RIS

    In 1987, published in Science, making a strong case for the role of “regional processes” in influencing species diversity in biological communities. Twenty-nine years after the paper was published, I asked Robert Ricklefs about his motivated to write this paper, the impact it has had on the field, and where he stands, currently, on what he said in the paper.

     (Questions sent by email on 15 August 2016; responses received on 19 September 2016)

     Citation: Ricklefs, R. E. (1987). Community diversity: relative roles of local and regional processes. Science 235: 167-171.


    Hari Sridhar: For the first two decades of your research career, your primary research interest seems to have been the evolution of avian life histories. This 1987 paper is one of your first on the topic of large-scale patterns in biodiversity. What triggered your interest in the latter at this point in your career?

    Robert Ricklefs: I had been interested in community ecology since beginning my graduate studies with in 1963. Community ecology was caught up in a new wave of excitement at that time, and was the primary emphasis of MacArthur’s students, including and . Mathematical modeling of ecological communities, including the development of community matrices to examine community stability was an important development of this period. Life history evolution also generated broad interest at the time, particularly owing to the work of and the controversy over ideas about reproductive restraint espoused by and , among others.


    HS:  What was your motivation to write up this particular paper?

    RR: The emphasis of community ecology during the 1970s and 1980s on mathematical modeling and experimental approaches naturally limited the perspective of many ecologists to local assemblages and short time frames. Although MacArthur is well known for his work in biogeography, he believed that one could develop an understanding of community ecology only by investigating spatially and temporally local systems. History was unique and unpredictable. Of course, many biologists, particularly those with an interest in the evolutionary relationships within, and diversity of, particular groups of organisms, took for granted that history and geography were important. Yet, their perspective was largely ignored by community ecologists at the time. Thus, many of these biologists welcomed the Science paper, but with the thought that “Well, we knew this all along.”


    HS: How long did the writing of this paper take? Where did you do most of the writing?

    RR: I wrote the paper 30 years ago, and some details of the circumstances have faded. Certainly the manuscript was produced in my office at the University of Pennsylvania, and probably relatively quickly. I had been teaching ecology for some years and had written on the subject, so the manuscript probably was written fairly quickly.


    HS:  In the paper you thank "R. Burton, H.V. Cornell, J. Diamond, R. Karban, R.T. Paine, S.L. Pimm, J. Roughgarden and N. Stoyan for comments". Can you tell us a little more about how you knew these people at that time, and how they helped?

    RR: These people were a combination of professional colleagues (, , , , [with whom I had spent a sabbatical]), department members (Burton), and former () and current (Stoyan) students, to whom I had sent drafts of the manuscript. Their comments were very helpful in providing as much balance as possible in a paper that grew out of a strong point of view. Several of the reviewers objected that too little credit was given to others who had expressed similar ideas. Yet, the large number of citations to the paper over the last 30 years suggest that a similar ‘sign-post’ paper was lacking.


    HS: Did this paper have a relatively easy ride through peer-review? Was Science the first journal to which this paper was submitted? Would you remember in what ways the final published paper was different from the first submitted draft?

    RR: A manuscript on a topic of my choice was solicited by Dr. at the Academy of Natural Sciences in Philadelphia and a member of the Science editorial board. Ruth was a wonderful mentor and promoted the careers of a number of young scientists in many ways. This certainly provided me a unique opportunity.


    HS:  How was the paper received when it was published?

    RR: The paper was welcomed by many biologists with similar views. Communication then wasn’t what it is now, and so I was glad to get a few letters from colleagues.


    HS:  This paper has been cited over 1800 times. At the time when you wrote it, did you already feel that this would have a big impact? Do you know what this paper mostly gets cited for?

    RR: Of course, I thought the paper was important at the time, and that it represented a departure from the direction of much of community ecology. It was probably the clearest and most prominently published (and most conveniently citable) statement that history and geography matter in ecology.


    HS:  What kind of an impact did this paper have on your career, and on the future course of your research?

    RR: The strong and mostly positive response to the paper certainly encouraged me to pursue further work on the historical and geographic contexts of ecological communities, although I continued to work on avian life histories. The paper directly led to my collaboration with on , published by the University of Chicago Press in 1993. The response to the paper also encouraged me to pursue my interests in , basically an historical/geographical hypothesis, in collaboration with , whom I met in 1989.


    HS:  Towards the end of the paper you highlight four steps that need to be taken to "regain a historical perspective and use it to resolve the major issues of community ecology":

    1. paying attention to developments in biogeography, paleontology, systematics, and evolutionary biology.
    2. studying the historical development of community ecology and reevaluating the conclusions of influential investigators.
    3. rigorously examining the hypothesis of local equilibrium by putting community convergence and the independence of local and regional diversity to the test.
    4. assimilating data on geographical distribution, habitat selection, and taxonomic status into the phenomenology of the community concept.

    Twenty-nine years after this paper was published, how well do you think community ecology has fared in each of these aspects?

    RR: There is no question that community ecology now fully embraces the large-scale temporal and geographic contexts of species distributions and local assemblages of species, and it is a more exciting field because of this. These contexts have largely stimulated current interest in global datasets of species distributions and functional traits, and have helped to further integrate evolution, biogeography, and ecology. Hypotheses concerning community development and maintenance are difficult to test, as we have seen in the case of ’s , but community ecology remains a vibrant and important (and optimistic) area of ecological research.


    HS: You say "The scales of population processes leading to local exclusion of species, and those of the evolutionary and biogeographical processes that promote species richness, remain to be determined". How much progress have we made in understanding the scales over which these different processes operate?

    RR: The predominant view at present seems to be that large-scale processes are felt locally. Integrating across scales has proven difficult, although phylogenetic analyses of local assemblages and species traits and distributions are providing new insights into the history and geographic context of local ecological communities. It is an exciting time!


    HS: In the Conclusion to your paper, you indicate certain approaches that will be useful in understanding historical and regional causes in variation in species richness: "comparative studies, statistical analyses of patterns, and "natural experiments"". How well do you think these approaches have been used in addressing this issue? Have there been other approaches that you didn't anticipate in this paper, that have helped in addressing this question?

    RR: The paper was written just as molecular phylogenetic analyses and phylogeography were becoming generally available. This has changed everything in the sense that one can now visualize something of the history and geography of species assemblages. New statistical tools are very powerful; large, global datasets have become available; approaches such as species distribution modeling, combined with genomic and gene expression analyses, have helped us to understand the geography of species. I am very optimistic.


    HS: Have you ever read the paper after it was published? When you read it now what strikes you the most about it, especially in comparison to the papers you write today?

    RR: I had not read the paper for many years, until recently in the context of responding to these questions. The paper reads as though it was written as a critique (it was!) on the predominant direction of ecology at the time. As mentioned above, these views were shared by many biologists, particularly those with a deep interest in the evolution and distribution of species in a particular taxon, including systematists, taxonomists, and biogeographers, who felt disenfranchised to some extent by ecologists. Most of what I have published is predominantly empirical or, in a few cases, theoretical. I have written few papers, like the 1987 Science paper, of a critical nature, although some of my papers in Ecology Letters (, ) and The American Naturalist (, ) have a similar feeling of addressing broader issues in community ecology.


    HS: Among all the papers you have written, would you consider this one of your favorites?

    RR: It is certainly one of the most important in the sense of its impact on the field and in clarifying, to myself, my thinking about community ecology. It has been gratifying to the extent that community ecology has encompassed the points of view expressed in the paper, although I believe this would have happened in any event. Thus, the paper was perhaps more a chronicle of changes ongoing in community ecology at the time.


    HS: What would you tell a student who is about to read this paper today? What should he or she takeaway from this paper written twenty-nine years ago?

    RR: I emphasize to students that historic papers can help us to understand the development of ideas and approaches in a discipline. Our ideas don’t arrive out of the blue, but rather develop over time through observation and inspiration. It is unfortunate that the early literature in ecology is becoming (inevitably) more remote to present-day students. Understanding how ideas (including bad ones) have developed in the past within a discipline, as recorded in the classic literature, provides a context for the development of new directions.




  • Post date: 5 months 3 weeks ago
    Citation for this post: BibTeX | RIS

    In 1999, , and published in Nature showing how the common cuckoo exploits the sensory predispositions of its host, the reed warbler, to obtain the same amount of care that the latter would give a brood of its own chicks. Seventeen years after the paper was published, I spoke to Rebecca Kilner about her motivation for doing this work and how it influenced her subsequent research.

    (Questions emailed on 26 July 2016; responses sent on 31 August 2016)

    Citation: Kilner, R. M., Noble, D. G., & Davies, N. B. (1999). Signals of need in parent–offspring communication and their exploitation by the common cuckoo. Nature 397: 667-672.


    Hari Sridhar:  After completing a PhD on "Parental investment in canaries and zebra finches" in 1996, you started working on the cuckoo-warbler system. What was your motivation to switch to this system?

    Rebecca Kilner: My PhD work was mainly an experimental analysis of the way in which nestling birds signal to their parents for food. I chose the canary as a model study system because I could breed it in captivity and so subject it to manipulations that wouldn’t have been possible in the field (at that time). It was a natural extension of this work to turn my attention to cuckoo begging behaviour. We wanted to know whether cuckoo chicks tapped into existing rules of communication between nestlings and parents, or whether they had a special trick for extracting care from their hosts. It turns out they just tap into the existing rules.


    HS: This paper has three authors. How did this group come together and what did each person bring to this project?

    RK: I started working on cuckoos when I was briefly employed by Nick Davies, in the months after finishing my PhD and before I started a research fellowship. He is arguably the world expert on cuckoos, and natural history and behavioural ecology in general, and he already had a post-doc, David Noble, working with him on a different grant.

    Nick and Dave did most of the hard work in the field, finding and checking hundreds of nests. My job was to design the experiments, to measure begging behaviour in the lab and to carry out the provisioning experiments with Nick.


    HS:  What was a typical day like for you during the summers of 1996-1998? Did you have help in field? Who was M. de L. Brooke who you thank for help in finding nests?

    RK: These were some of my happiest days as a biologist, mainly due to the wide-ranging discussions Nick and I had about biology as we sat for long hours in our deckchairs and counted provisioning rates at the warbler nests. I also spent a lot of time in a shed used by the ringers at . This was less fun, but made more enjoyable by regular visits from Ralph, an old Fen man who kept geese and ducks in the neighbouring field and who always had a good story to tell (“Saw a baby mink today. Got it with my pitchfork”). The shed was also well-positioned for access to the ice-cream van.

    is the Strickland Curator of Ornithology at the Cambridge University Museum of Zoology. He did the field experiments on cuckoos and reed warblers with Nick Davies in the 1980s that have now become in the field of co-evolution, setting the benchmark for quality in this research area and laying the foundations for all the cuckoo work done since. Mike helped out by finding nests and letting me sit in his freezing cold kitchen to measure nestling begging behaviour (The chicks were fine because we kept them in heated nests but I had to keep popping outside to warm up!). He also collected some of the provisioning data we used in our analyses during his time working with Nick in the 1980s.


    HS:  In the Methods you say you used "old Turdus nests" placed over the reed warbler nest in the brood size manipulation experiment. Where did you source these Turdus nests from?

    RK: Nick found them in his garden and in the Botanic Gardens in Cambridge.


    HS: Does Wicken Fen still serve as a field site for brood parasitism research? When was the last time you visited this site? Has the place changed from the time you did this study?

    RK: Yes, Nick still works there every summer. I go from time to time with my family. It has changed a bit since we worked there. It’s much larger and more managed. There are boat rides on the Lode and a teashop now as well. It was more rustic when I worked there.


    HS: You acknowledge "C. Thorne and the Wicken Fen group for research facilities". Can you tell us a little more about who these people were and how they helped?

    RK: These people ring birds regularly at Wicken Fen and allowed us to use their shed as a field lab for measuring begging behaviour (see above).


    HS: Who did most of the writing for this paper? How long did the writing take?

    RK: I’m probably biased but my memory is that I did a lot of the initial writing and drafting. It was greatly finessed by Nick, though, and we spent quite a while discussing how to bring the different parts together to tell the story. We planned the broad outline of the story before the field season in 1998, and spent that season filling in the gaps. We finished collecting the data at the end of July and submitted the paper in November. 


    HS: You thank a number of people for commenting on the manuscript. Can you tell us how you knew each of these people?

    RK: The people we thanked were: , who I shared an office with and who is an outstanding field biologist; , a talented behavioural ecologist, who was a post-doc at the time in Cambridge - I started working with her on Australian cuckoos in 1999 and the collaboration continues to the present day; and who is a theoretical biologist and whose work has been hugely influential in shaping the way we think about the evolution of animal signals. He was a post-doc in Cambridge too at the time, and his papers inspired a lot of our experimental work.


    HS: You thank B. Grenfell for producing Fig. 7. Can you tell us who this was?

    RK: This is the eminent epidemiologist FRS. He was a lecturer in the Department of Zoology in Cambridge at the time - he is at Princeton now.


    HS: Did the paper have a smooth ride through peer-review?

    RK: Yes, amazingly.


    HS: Was Nature the first place you submitted this to?

    RK: Yes.


    HS: How different was the published version from the original submitted version?

    RK: Not that much, as I recall


    HS: How was the paper received when it was published?

    RK: Well, I think. I gave a few seminars about the work which went down well and it got some nice coverage in the media in the UK


    HS: Did this paper have a major influence on your career?

    RK: Almost certainly. It was very exciting to get a Nature Article published when I was 27. It will probably never happen again! It helped me take the next steps in my career towards becoming a tenured academic.


    HS: How did it impact the course of your future research?

    RK: In two very obvious ways. First, it made me wonder why cuckoo hosts don’t reject cuckoo chicks given that they can reject cuckoo eggs. This is the problem I worked on next with Naomi [Langmore]. (a complete shock at the time). We still don’t know exactly why reed warblers don’t do this too, but I think we are closer to solving this problem.

    Second, it made me wonder why other brood parasitic chicks, like cowbirds and vidua finches, don’t kick out host chicks in the way that the common cuckoo does. To answer this question I teamed up with and . - this is why they aren’t kicked out at hatching. The cuckoo can’t afford to do this. Unlike cowbirds, it is much larger than its hosts and would probably starve if it shared food with the host nestlings.


    HS: In the paper you say "the amount of food supplied by parents to young is likely to be the source of a conflict of interests between the two parties". Did this paper in some way motivate your later work on parent-offspring conflict?

    RK: My work on parent-offspring conflict started with my PhD research, in fact, and still dribbles on...


    HS:  Its now 17 years since this paper was published. Would you say that its main conclusions are still, more-or-less, correct?

    RK: I think so. Rather than calling like a brood of chicks as the common cuckoo chick does, it displays fake gapes - bare patches of skin on its wings that simulate the gapes of other nestlings. So it faces the same problem we identified in the common cuckoo, but has evolved a different signalling solution.


    HS:  If you were to redo these experiments today, would you do anything differently, given the advances in technology, ecological theory and analytical tools?

    RK: I’d probably analyse the data in a more sophisticated way


    HS: In this study, you derived two regression equations experimentally - 1. Relating chick need to begging signals; 2. Relating begging signals to parental behaviour. This, you said,  provided, in principle, a way to test the prediction that parents supply chicks with exactly the food they demand, but which wasn't possible then because the "the analysis is beyond our reach". Is such an analysis possible today?

    RK: No, unfortunately. The problem is that the equations are not in the same units and so cannot be directly related to one another. I can’t see a way round that.


    HS: You conclude the paper by saying "the constraints of eliciting a high provisioning rate alone, or of losing food in sibling competition, may mean that we never see brood parasites being fed at the high rate we might predict". Is this still the case?

    RK: I think so - and our cowbird work supports the concept of this trade-off.


    HS: Do you know what this paper mostly gets cited for?

    RK: No.


    HS:  What would you say to a student about to read this paper today? What should he or she take away from it? Would you add any caveats?

    RK: I hope mainly that they are excited by the natural history. And that they can see it is possible to reach some quite sophisticated conclusions by thinking clearly rather than simply using fancy techniques or analyses.


    HS:  Have you ever read the paper after it was published?

    RK: No, I can’t bear to read anything I have written! I spend a long time working on each paper, but once it is gone, it’s gone for good and it’s time to think about the next problem.


    HS: Would you count this as one of your favourite papers, among all the papers you have published?

    RK: I like this paper because we had so much fun collecting the data and working everything out bit by bit. We ended up with a very different set of thoughts to those we started with. I very clearly remember working out how to start thinking about multiple signals with these data - I was in the shower of all places. And the excitement of putting that idea into practice still dripping wet and barely clothed.

    I don’t have a favourite paper, but the ones I like most combine these ingredients - fun designing experiments and collecting the data, puzzling patterns that don’t make sense at first, the thrill of the penny dropping when you realise what is really going on, and the excitement of writing it up and sharing your excitement with others.





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