“I was not invited by the journal to write the paper. I submitted a proposal three times in successive years before it was accepted.”

“I wasn’t a birdwatcher from a young age. However, I did spend a lot of time in the mountains and in conifer forests when I was young. My passion for birds started in college. Then in the summer before starting my PhD, I helped a friend with his PhD, and crossbills were quite common in that forest. I got to know them a little bit more. So, I had some feel for crossbills and their habitats, and knew enough to believe they could be interesting to study.”

“I wasn’t certain whether I was going to go into Evolution or into Community Ecology. After I started working on this project, I was still trying to make up my mind. I had an opportunity to do research on fishes in the Amazon. I was in Brazil for my second field season and it was a total catastrophe because the government prevented our research team from going out into the field. So I spent about three or four weeks in Manaus writing out the equations that finally became that paper.”

“I will suggest they read one paper that is older and one paper that is more recent. I would suggest that they went back to some of the original ideas, to some of Preston’s ideas in the 1960s about how the number of individuals is related to the number of species. That had a strong influence on my thinking. I would also suggest that they go and look at some of the really cool new studies that have been done, where they’ve tried to use some really large databases to test some of these ideas. I was using experiments in a limited number of tree holes to test the underlying premises of the “more individuals hypothesis”, but structural equation models also allow the testing of on mechanisms on large observational datasets. A nice synthesis of both experimental and observational tests of the more individuals hypothesis is the 2018 Ecology Letters review by David Storch and colleagues.”

“I worked alone except for one day during the trapping period when my sisters were in town and they wanted to come with me. That was a bad idea. I was doing the removal experiment for recruitment estimation, which meant I had to move the captured mice to another woodlot several km away. My sisters seemed incapable of opening a trap without letting the mouse go, so this created a bit of a blip in my data.”

“I worked in Tanzania and Uganda during my thesis on Colobus monkeys. And, while they were very interesting, the problem was that they live in the canopy, between 70 and 120 feet above your head. Your capacity to recognize individuals is quite limited. Your capacity to collect biological material from them is quite limited. Your capacity to measure food availability is quite limited. And having spent three years working on this, for my next project, I wanted both to be placed in the UK rather than overseas, and I wanted a more tractable species where one could actually get access to the animals, where one could ideally collect biological material for individuals, where you could measure the food supply, and where you could follow the survival of individuals throughout their life. And that immediately made me realize that really one wanted a terrestrial species, and you wanted a terrestrial species that was visible and lived in a habitat where you could actually see what was going on. And red deer in Scotland live in open environments. I’d had experienced them previously when I worked for Roger Short taking a film of his work on the reproductive physiology of red deer. So, I knew about it. And red deer are one of the principal grazing species throughout much of the highlands of Scotland, so there’s an economic interest in them. And all of those made me realize the red deer were a good animal to work on.”

“I would ask them [students reading the paper today] to read it, and when reading it to imagine me working there, on foot, more than 40 years ago. And I would ask them to try not to find fault with it, because you can easily find fault with it, in retrospect.”

“I would ask them [students reading the paper today] to think about its [the paper's] importance in an historical context. What they should take from it is that it built long-lasting conceptual and empirical bridges between two formerly disconnected evolutionary arenas.”

“I would live in Mexico for much of the summer. One summer I rented a very small cabin in Cholla Bay with Pete Raimondi. There was no running water or power. It was very hot during the day (>42 degrees C), and very humid. We would often sleep on the roof of our cabin to catch the breeze. The mosquitoes could be ferocious, so we eventually got some mosquito nets. So, a lot of what we did was just try to survive. The locals in the town would say that there are about four days each summer that no human can survive. I was there for those days. As far as research, I would work the low tide in the morning and evening. At the beginning of the Spring tides, I would be on the reef by 4:30 or 5 AM, and work until the tide came in at about 10 AM. I would sleep in the afternoon, and then work the low tide again in the evening. The evenings were beautiful. I would make a point to watch the sunset every night. During the semester, I would drive from Tucson to Puerto Penasco on Thursday night, and work through the weekend. Much of the time, I slept in and worked out of my truck at Pelican Point. But there was also a house near Puerto Penasco, which we could stay at, and sometimes I would stay there. The house had power, and it was often full of interesting people, mostly marine biologists. There were many parties.”

“I would say it is a good example of how to link theory and experiment, but also that by today’s standards it is not a very sophisticated piece of work and much has been done since then to develop both the theory and experimental techniques.”

“I would say it’s just a small study that illustrated a particular point. And it’s not the last word on the subject by any means. There’s still a lot of analysis to be done. And many other systems and the conservation angle are still out there to be explored. I guess I’d say that.”

“I would say that the questions asked in that paper remain relevant, but the approaches needed to answer them will need to be more multifaceted compared to what I did. We need descriptive work, experimental work, and modelling in order to understand the structure and functioning of trophic networks.”

“I would say the statisticians have not shaped up at all. And I think that applies to the professional statisticians who teach statistics as well as other scientists who also often are teaching stat courses – biologists, psychologists, so on. The stat books, including some of those most commonly used by biologists, often completely ignore design. And that’s a major flaw in Sokal & Rohlf, probably the single biggest flaw of many that are in that book. I’m not sure if I published this or just commented on it, but there is a basic problem in the interaction between statisticians and people in other disciplines: statisticians often have a professional interest and professional incentives to develop fancy new methods for very special case type situations, and have no incentive to try to help people stop making simple errors in papers. They think that’s a little bit below them. And they’re not interested, they don’t enjoy reading critical reviews of statistical practice, like the sorts of things I’ve written. The editors often have a hard time because the statisticians are saying, “Well, yeah, these ecologists are making all these stupid mistakes, and that’s what Hurlbert’s talking about in this paper, but you know, they should clean up their own mess. You don’t need statisticians in order to avoid pseudoreplication.” Or, something of that sort. So the books remain not very good.”

“I would say this paper was mostly catalyzed by one-on-one discussions followed by drafts and notes exchanged between us. Of course, we also had phone calls, but I think the physical presence of the three of us was necessary and important because we were struggling to crystallize what we meant. It really helped to be conversing, drawing all sorts of figures and conceptual frameworks on the board, and making a list of all the examples we knew about from the literature that may or may not be [ecosystem] engineering. At the same time, it wasn’t something where we could just get together for a couple of days and bang it out. I also don’t think it was very amenable to what today is a common way of writing papers – exchanging endless drafts among large groups of people and getting comments and feedback via email. Maybe it was representative of that era, but maybe it was also representative of the challenge. We knew what we wanted to do but we didn’t know exactly what that was. That meant there was a lot of iteration, going to and fro to try to crystallize it.”

“I would suggest to read it together with some of the key papers that followed in this field, because by putting it into a historical perspective you get a better idea how science really works. There is a tendency nowadays to lament about the fact that science is not reproducible. There are certainly some important issues that are worth discussing in this context, but part of the discussion bores me because it seems to be based either on false ideas about how science actually works or on unrealistic ideas about how it should work. There is no such thing as a perfect study. Studies are always done in a particular context and not always will the results be generalizable across contexts. That is especially true in our field, where we are working within a complex and variable ecological context. I think it is important that students learn, at the earliest possible stage, that science is not about writing the definitive paper on a particular issue, and that research is not about going in a straight line from point A to B. I like the way Stuart Firestein puts it, in his wonderful little book “Ignorance: How it Drives Science”: science is like “looking for a black cat in a dark room without knowing that there is a cat in the room”. So, it’s about being curious about a phenomenon and studying it from this or that angle, through careful observations or experiments. It’s about drawing conclusions that seem most reasonable given your data as well as your knowledge and thoughts and those of others at that time. And it’s about admitting limitations or weaknesses and openly discussing things we still do not know. Things are rarely black-and-white. Coming back to the evolution of extra-pair paternity, there is still evidence in some systems pointing to genetic benefits, but there are also studies that suggest that female extra-pair behaviour might even have evolved in the absence of benefits, simply because of strong selection on male extra-pair behaviour. There is no simple answer, and it remains interesting, so if a student is interested, he or she can still go out there and discover a black cat, or perhaps it will turn out to be a blue bird.”

“I would tell her that this paper is very difficult to read, but it has a lot of interesting information that might be useful to her. I would explain the value of story telling as a means of understanding nature, and that there are several interesting stories in the paper. I would suggest that as she reads it she copies the table of contents and lists the various vignettes or stories in the paper, and at the end see if she can synthesize those that are of interest to her into a big pictures story that makes sense.”

“I wrote it longhand on lined tablet paper in pencil, then edited the longhand first draft and typed it up on an old electric typewriter I had scrounged from the Biology department office. It might have been the last paper I wrote that way. I think I got my first desktop computer right around that time, and would have switched to word processing then.”

“I wrote this paper in 1997 and then continued rewriting it and repeating the basic experiment for five years as the paper was repeatedly rejected by at least five journals. [...] I revised the paper many times as I attempted unsuccessfully to publish it.”

“I, actually, got the results in 1988. But the inconvenient event at the time was that I was getting a divorce, so I wasn’t able to work on it as quickly as I would have otherwise.”

“I’d say: Come with me into the woods, watch these butterflies displaying, think of the sorts of questions you would ask, think critically about whether the experiments I did provided convincing evidence [] and then think critically about whether the interpretation I gave from the current theory at the time would be a useful interpretation today.”