“One day as I was walking across an old field, a beetle flew over my head and landed on a small shrub in front of me. And an ant ran after the beetle, trying to grab it, and the beetle then flew away. That sort of stuck in my head, and later on the same day I walked back by the same plant and looked closely at it. There were ants all over the surface of the plant. I thought that that was kind of curious and I noticed that the ants were going in and out of big thorns on the branches. I took one of these trees home to dissect and see what was inside the thorns and so on. So, I was looking at the ants like ants, without thinking about anything more. Well, maybe a week later I cut down two trees in a pasture, to take one of them home to dissect again. The other one, by accident, I just left there, by the stump. So there were two stumps about a metre apart, one with a tree cut down next to it and the other with no tree. About six weeks later, I walked by that pair of stumps and noticed that the stump that had no tree lying next to it had produced some sprouts but they were in terrible condition. They had been eaten down to almost nothing. Whereas the stump that had the cut down tree crown next to it had a beautiful one metre tall sprout growing out from it with beautiful leaves and very good condition and ants all over this sprout. Well, that caused me to realise suddenly that what I was looking at was an interaction where the ants were protecting the tree. It wasn’t just an accident that there were ants there. They were very involved with the tree. So I picked that up to study for my dissertation. And my dissertation basically consisted of removing the ants from thousands of these trees.”

“One of the things I remember with great pleasure is watching the reed warblers reject the eggs. You can make a little channel through the reeds from the bank and just sit quietly, and the reed warblers will come and sit on the nest. We saw both males and females pecking at the model eggs. So, it’s very clear that both sexes rejected eggs. At one nest the male was quite happy with the odd egg in the nest, but the female decided she didn’t like it. She started to dismantle the nest to build a new nest nearby, while the male continued to incubate. You could imagine him thinking, what on earth is she doing? And of course, once the nest was dismantled, he had to agree to the move! I just remember that as a bit of natural history that I found absolutely fascinating, that males and females both reject, but they wouldn’t always agree on whether rejection should take place or not.”

“Overabundance of fleshy fruits in autumn-winter, and of overwintering birds that feed on them, are two obvious features of evergreen Mediterranean-type scrublands and forests in southern Spain. It was obvious to local observers, yet remained unreported in the ornithological or ecological literature.”

“This came about completely by chance. I had just finished my PhD, a study of the behaviour of a little bird, the pied wagtail. My pied wagtails defended territories along a river, and I noticed that every so often, a territory owner would leave his territory to feed elsewhere, particularly on days when there wasn’t much food on the territory. But periodically throughout the day, he would keep coming back to check if there was anyone intruding on his territory, and if there was, he would chase them off. I was very interested to know why he was doing this. I wondered if he was trying to prevent any newcomer spending sufficient time on the territory that it would get to learn its characteristics and, in effect, think this is a jolly nice place to live. If the owner came back periodically and chased off a newcomer before it had time to learn about the territory, it would be easier to get rid of him. To test this idea, I wanted to catch the owner and keep him away for a sufficient length of time for a newcomer to learn the characteristics of the territory, then put the original owner back and ask if he would then find it harder to win back the territory. I tried for a winter and failed completely simply because the birds were too hard to catch. I was then living in a little chalet in Wytham Woods, on the edge of Oxford, where David Lack started his famous studies of the great tit. I had a spare summer because I had just finished my thesis and my next job didn’t start till the autumn. This was 1976, so 40 years ago, and it was romantic living up in the woods. Every day was sunny which was highly unusual for England. People still remember that glorious summer. I think we had a three month spell with cloudless skies and the wood was full of butterflies. And I just noticed some butterflies doing little spiral flights in sunny patches, and I thought, well, that looks like territory defence. Maybe I can do the experiments on them instead of the wagtails because butterflies would be much easier to catch. [...] The whole thing came through natural history curiosity and serendipity, I guess.”

“This was in the very early days of Conservation Biology. For obvious reasons, a lot of people were interested in how long small populations would persist. It is a very straight forward management problem. If you have a tiger reserve that has only 4-5 tigers in it, how long will that population be expected to live? It obviously has something to do with the generation time of the animal — individual tigers live a long time. But even if you are measuring generation times, how many generations does a small population persist? I knew – because I had spent a lot of time when I was a teenager on some of these islands – that, off the coast of Britain and Ireland, were a large number of islands where birdwatchers visited very routinely in the spring. These birdwatchers not only kept lists of how many species they saw and how many species were breeding there, but they had done so for 30-40, in one case 50, continuous years. So, one could directly answer the question of how long these small populations lived.”

“Watching the birds was extremely interesting and stimulating. There was always something new to see, and many observations would make you ask ‘why are they doing that’? Some observations would provoke analyses that contributed to a paper. An example of this was the observation that certain females would sit by particular males and engage them in courtship at times when another female tried to approach them.”

“We could only do experimental pollinations of those figs when individual figs (syconia) were in two specific stages: when some were releasing pollen-carrying wasps, and others were receptive to pollination. This was rare and you had to be ready for it. When we sensed that this was coming, we would take figs about to release wasps into the lab [...], and leave them in covered petri dishes. The wasps leave the figs, and mill around in the dish. The dish would then be taken into the field, and individual wasps picked up with a tiny paintbrush and placed on figs that looked receptive. If we were right (the wasps knew; we couldn’t tell), then the wasps would burrow into the fig.”

“Well, actually, it was serendipitous. I went out to the islands to study the behavioural ecology and genetic structure of the island fox. And while I was there, I started to see some mortalities of foxes. I had worked with bald eagles in the past, and had figured that golden eagles, which were irregular visitors to the island, were taking foxes every now and then. And then I started seeing a steep decline in the foxes while I was there, so I just happened to be at the right place, at the right time, to be able to identify what was going on.”

“Well, I have always been a bird watcher and have observed and wondered about this behaviour numerous times. Tony and I first met at a conference in 1996. In fact, at that conference, when I first suggested to him that jays might have memory he was completely dismissive. He said: “I can’t think of a single reason why they would need it”. And I said “Well, what about the fact that they hide perishable food? Wouldn’t it be important for them to be able to remember when or how long ago their cached their food, in order to know when they needed to recover their caches of food?” He didn’t know anything about the caching of perishable foods and so he said: “Oh gosh, I hadn’t thought about that”. So then we went away and spent much of the rest of the conference talking and discussing. I told him what I knew about the behaviour of the birds in the wild, from my observations of them, and it was at that point that he said: “Oh well, I just made an assumption, I didn’t know about this”. And I said “Well, this is something that we could test empirically”. And he said: “Absolutely, yes”. So then we got into a collaboration designing experiments to test whether or not the birds could remember the “what, where and when” of past caching episodes.”

“Well, when I started to work with frogs for a Master’s thesis, before I went to Cornell to do my PhD, the dogma was – most of which was true – that frog calls evolved to indicate the species [...]. And that females were under strong selection to mate with males of the same species. That’s certainly true. And then when I went to Cornell and started working with bullfrogs – I was not working with calls then; I was studying territoriality – I was struck by how variable their calls were. I mean a bullfrog call sounds like a bullfrog call, but I could clearly tell males apart. I would hear a male and know that he was on a neighbouring territory the night before. That he’d moved over. That’s how I became interested with the frog call, as it had to do with mate selection within a species.”

“What I found interesting was that I could go to any wet forest habitat on any island, and I would almost always find four species of the spiny-legged spiders: one that’s green and lives under leaves, one that’s large brown and lives on tree trunks, one little brown that lives on twigs and one maroon that lives on mosses. It was just so striking that you almost always get the same set of forms, or “ecomorphs”, on each island. The green ecomorphs on one island look just like the green ones on every other island, and likewise the large brown, little brown, and maroon. So, at the meeting in Australia, I talked about the close affinities of the green ones across islands - surely the green ecomorphs must either be the same species or be very closely related (and likewise the large brown, little brown, and maroon). But then, you know, we got a hold of the molecular data and it told us a totally different story, that the different green ecomorphs are not their own group (and likewise maroon ones and the brown ones). Rather, they have independently or semi-independently evolved the same set of ecomorphs on each of the different islands. So it was really this kind of incredible realization that these things that looked as if they were so similar and then to find that actually they were not that closely related. That was fairly mind-blowing to me.”

“When I was an undergraduate student, I got the chance to go on an ornithological expedition to the Andes in Ecuador, the purpose of which was, basically, to do a survey of all the cloud forests. At that time, I became interested in questions that we now call Macroecology. I read a lot of the literature of people like John Terborgh and Jim Brown, and since we were working in mountains, I particularly read everything I could about mountains and diversity patterns. The literature was unanimous that it was a universal rule that species richness declined with altitude. So, with this background, we went on these expeditions. We basically spent 6 months in pouring rain in the cloud forest. It was fabulous; the diversity around us was just astonishing. When we were done with that – this was way back in the time of no emails – we posted a snail mail back to our supervisor in Copenhagen. We were four people in this expedition, and in our mail we said that since we had now worked six months, would it be okay if we stayed on and made a venture down in the Amazon. At that time, the Amazon was thought of as the richest place on earth and we really wanted to see it. We waited and a month later we got a reply saying – Yes, we could go down to the Amazon. We went down and I have never been so disappointed in my life! I expected to see so many more bird species than I saw in the cloud forest, but there were fewer. I was shocked because everything I read and all the textbooks told me that I should find more species in the lowland. So I started to think about what was wrong – Was it very unusual? Was it because we couldn’t find the species? – this was kind of simmering in my head while I was doing my Master’s degree on other things.”

“When we started to work on them our goal was to see how flexible this tool use was, and how sensitive it was to the needs of the task. In order to do that we placed two wires, one which was bent and one which was straight, on top of a vertical tube which contained a bucket in the bottom. We were trying to see if they [New Caledonian crows] would pick up the bent one to collect the bucket. In the experiment we had two individuals close together – a male and a female. The male was bigger and dominant over the female. What happened was the male picked the bent wire and took it away. The female, Betty, was left with only the straight wire with which she tried to retrieve the bucket but failed. What she then did was to basically jam the wire against the base of the tube and bend it [...] the first observation was made by my student Alex Weir, who became the first author of that report. Alex Weir had started his PhD six months earlier and so this was practically his first experiment [...] one day he came to us with this video. He said: well, my experiment didn’t work as planned because one of the crows took away the bent wire! Then this is what happened. And he showed us the video of Betty bending the wire. When I saw that I was completely bowled over. It was unbelievable.”

“When you feed a monkey group, the dominant monkey will try to grab everything. To avoid that, you hold a treat in one hand, off to the side, and try to tempt the dominant monkey over there, while not letting him have it and simultaneously feeding the other monkeys with the other hand. I was doing that with the peanuts and the dominant male, Ozzie, finally got frustrated with this. He ran back to the inside area of their enclosure and came back with a piece of monkey chow. He pushed it through the fence at me and tried to get the peanut. When I didn’t give it to him, he went back inside, where they had just gotten their fruit and vegetable trays, and returned with an orange peel. Then he did the same thing, pushing the orange peel through the fence at me. Again, I didn’t give him the peanut. Then he went inside again and came out with a whole quarter of an orange, which is quite large, of course, and he pushed that through the fence to me. I finally gave him the peanut, but it got me thinking, because I was relatively certain that if I walked up to Ozzie and offered him a choice between a single peanut and quarter of an orange, he would chose the quarter of the orange. If so, it was possible that he wanted the peanut because everybody else was getting one. Now, oranges weren’t a terribly limited resource, because they had just gotten their fruit and vegetable tray, so he could have gone inside and gotten another orange. But it was a very interesting interaction, and I really wanted to know whether my thought was right.”

“Yes, I still remember that day in an ash tree! Butterflies defending sunspot territories sat on low perches, often on brambles or other leaves in the ground layer. Butterflies that were intruding came down from the canopy. I noticed that the canopy males searched for females in a different way. Whereas the sun spot males perched in the sunshine and waited to inspect things that passed by, the ones up in the canopy were patrolling. The canopy was more or less completely in the sun, so perhaps the best thing to do was to just patrol around and try and find females by active search. On days that were cloudy, but still warm enough for the butterflies to be active, I noticed that all the butterflies were in the canopy patrolling. These different tactics for searching for females were fascinating. What I wanted to test was why patrolling males were so keen to get sun spot vacancies that arose. Was the woodland floor the best place to look for females? This is why I sat up in a tree all day! I simply scored the number of females that visited sun spot territories below, and the number of females that I saw being harassed by patrolling males above in the canopy where I was sitting. I found that the sun spot males encountered many more females than the canopy ones. Though statistically the evidence wasn’t very strong, together with the behaviour of the males, it convinced me that the males were competing for best places to look for females. Another very important finding was that because territory vacancies arose frequently, most of my canopy males got a sunspot territory in the end. This suggested to me that a sun spot wasn’t an incredibly valuable resource, unlike my pied wagtails where only a small proportion of the population held territories. Here, it was almost like seats on a bus – everybody had a turn, if only they waited patiently for a little bit.”