Interview with Dr Rohan Clarke

By Tony Hunt

30 July 2015

Dr Rohan Clarke lectures in Ecology and leads the ResearchEcology group in the School of Biological Sciences at Monash University.  His research interests focus on the ecology of Australian fauna, especially birds and the management and mitigation of threatening processes. Within these areas of interest, research is conducted at a variety of levels from organismal ecology to ecosystem ecology.


Tony: I wonder if you could start by giving me a bit of a background on how you originally came to an interest in birds and how that led you to becoming a professional ornithologist?

Rohan: I guess I’ve always been interested in birds. The bits I can recall are that I bought my first pair of binoculars when I was in grade six – so I guess that would make me about 10 or 12 or thereabouts? – and we had a family trip around Australia, taking the middle term off school, and that was pretty formative in terms of seeing a great diversity of birds; at that point I was already very interested. I got into bird banding with the Victorian Wader Study group when I was about 15 or 16 and that was also very formative, as a group like that was willing to take very keen but also very inexperienced people under their wing and train them up. On the first outing we caught an amazing diversity of species and despite the fact I was on my first trip I was employed as a runner and so took all sorts of birds to the banders and watched them working.

Tony: That’s a great experience for a young person to have, isn’t it?

Rohan: Yes, it’s a great hook, and so I was quickly hooked! I was already pretty engaged anyway, and so from then until at least some time when I was in University, when other things started to get in the way, I was a very active bander in the Victorian Wader Study group, going on almost every weekend trip, and I guess that’s where I really cut my teeth on bird banding, and bird research more generally as well. I already had an interest in birds but that got me involved in data collection from quite an early age.

Tony: It can be quite a leap from bird watching to structured research.

Rohan: Absolutely. And I think the Wader Study group is particularly good in that space, because they also exposed you to publication of data all that time, from articles in the VWSG Bulletin right through to articles in internationally-recognised journals, so pretty much every time we got together there was something being published in those sorts of publications, it didn’t matter at which level, so you saw the whole process from start to finish.

Tony: That’s fantastic, isn’t it?

Rohan: Yes, so even though you’re not actually writing the papers you could still actually see the output of all your hard work in the field and you could really feel a part of it.

Tony: That’s one of the really great things about bird banding, it does seem to provide a bit of a bridge between amateur birding and serious ornithological research, that’s accessible to both professionals and amateurs.

Rohan: Yes, absolutely. Although there seems to have been a bit of a shift in the numbers of people that continue to band compared to what there was perhaps twenty years ago, that crossover is still there and it provides an opportunity for new people to enter the field.

Tony: I’ve heard a number of people comment on the changing demographics of bird banding, but I’m not sure why that might be?

Rohan: (Laughs) I’m not sure either! But I do have some theories, not necessarily grounded in real data though.

Tony: You’re amongst friends Rohan, you’re allowed to speculate.

Rohan: (laughs) Yeah. I suspect that one element that is likely in the reduction in the number of banders is simply the change in policy that was in place for a while there where you had to pay for your annual banding license. It may not have changed the number of active banders all that much but I think it certainly trimmed out a lot of the inactive banders. So at least on paper there was a rapid reduction in the number of banders out there. It may have also reduced the number of less active banders who only did a small amount of banding, because it would have made it harder to justify maintaining a permit under those conditions.

Tony: There also seems to me to be a bit of a gap between the older banders and the young ones, with not many in between.

Rohan: Yes. Well that may just reflect life of course (laughs), in between for most people there’s a lot of other stuff like families and careers and everything else. It seems to be much the same sort of distribution in birdwatching, certainly on pelagic trips in many cases there are numbers of younger people and older people, with not all that many middle-aged people participating in those sorts of activities.

Tony: Let’s move along. Could you give us a rundown of what your research interests are – what aspects of ornithology you have a particular interest in?

Rohan: I come from a fairly applied and conservation-focussed background. I did a PhD on Black-eared Miners, and before that I did some work on the behaviour of honeyeaters, so most of my research is reasonably applied and most of it ideally has some kind of link back to conservation benefits for birds. The very broad area that I’m interested in mostly now is the movement ecology of birds and how that might actually affect management. But in saying that, I’m one of those people who has a pretty broad or diverse portfolio when it comes to research interests in that space, I’m not a person who settles on, say, muscles of fruit flies (laughs) as a topic, I’m fairly broad and that’s ultimately reflected in the sorts of projects I get involved in as well. They use birds as models and most of them you can link back to some sort of management issue, typically conservation-orientated rather than, say, management of pest species, and linked to some sort of aspect related to their movement. In some cases small levels movement, in species such as Mallee Emu Wrens, which we don’t think move about very much at all; through to large scale movements of migrants and how you might manage and better conserve migrants in landscapes – looking at species such as Regent Honeyeaters.

Tony: That’s very interesting; and reflects a number of conversations I’ve had recently with other ornithologists, basically around the notion that we really know very little about the movements of many birds in the context of the Australian landscape; and what we do know is often derived from a very large amount of inference connecting what is often a tiny amount of fact based on relatively small numbers of observations that are very scattered in both space and time. But it does seem we are now entering a potential golden age based on the increasing availability of really tiny tracking devices – I saw an ad last week for one that weighs barely more than a gram – and while a small amount of working has already been done using these, presumably there is still literally tons more to be done.

Rohan: Yes. The technology already exists, and the two critical components are the size, which translates into the weight being carried by the bird; and the cost. And these are both coming down, as you say there have been ads in the past couple of weeks for ridiculously small units, some of which communicate to satellites, others that use GPS that is either UHF downloaded or pings the data to a satellite after 30 or 60 waypoints have been collected. We’ve probably been right on that cusp for nearly a decade in the sense that every year a new tool that comes out that allows us to do another bunch of things. It depends a little bit on whether you’re at the front of the wave in trying to use the techniques, in part because they’re novel; or whether you’re sitting back a bit and waiting a little to make use of them when they’ll be a bit cheaper as the novelty wears off and costs come down when production kicks in. So yes, I think it’s got the potential to be a game changer; and if anything there’s going to be ethical considerations about how many of these things we should be putting out, because they come at a greater cost to the bird than just a straight metal band.

Tony: Indeed, and I guess that will be one of the challenges for the future, which is a topic we’ll come to shortly. Just out of interest, where is the state of the technology up to currently? Have we got to a device that, say, a large honeyeater could carry yet?

Rohan: Oh, absolutely. There was something just published in Nature in the last month or two*, on one of the small American thrushes I think – maybe a water thrush, or perhaps an Ovenbird? – and they put GPS trackers on these birds that were on the order of a couple of grams. The devices had the capacity to record about 30 or 50 waypoints, and they set them up so that they recorded waypoints after a couple of months then deployed them on birds that were just getting ready to migrate. The equipment didn’t record any positions for a couple of months and then recorded their positions after they had migrated, then when they returned to their breeding grounds they were recaptured and the equipment was downloaded to reveal their wintering location. These sorts of units would easily fit on our medium to large honeyeaters.

Tony: Which is pretty amazing when you start to think about birds like Blue-faced Honeyeaters, or Wattlebirds or Friarbirds, or any of those sized birds.

Rohan: Yes, I guess the 5g satellite tags that have been around for a few years now, in theory can fit on a bird that’s about 110-120g size, so there might be a couple of species in that size at the upper end of the honeyeaters would already fit that so a harness attachment and a satellite tag that’s pinging back a position every day , but were already well beyond that and so were down to half that mass with GPS tags and some of these tags now communicate to satellites so it’s not essential to recapture the bird to be able to retrieve the data.

Tony: Yes, because I guess that would be one of the challenges in Australia, because we’re not looking at where is their wintering ground and then they’ll come back to us next summer, it’s that once we let them go where do they go? Because we might never see them again.

Rohan: Exactly, after they fly away do they just fly over the hill and breed there, or if your hill is in Victoria do they fly over the hill and go to southern Queensland and spend a big block of time there? The really interesting nut to crack is how do they respond to resource availability – being rain, or nectar or whatever – because that’s the great thing in our environment, that’s the variability that we don’t necessarily see to the same extent in some of these other flyways where it’s mostly about looking at migratory pathways rather than how birds use entire landscapes that are less predictable.

Tony: Yes, so once we have some real data it might almost rewrites the landscape in our thinking about these birds. It’s a very exciting time.

Rohan: Yes. It has very, very significant applications for management too, for example with Regent Honeyeaters if we learn how they really do perceive and move through their landscape that may have a very direct application to how you might go about trying to restructure that landscape to help preserve them.

Tony: Well that presumably might apply to other endangered birds like Plains Wanderers, which might be about the right size too.

Rohan: Yes, they’d be close.

Tony: I certainly think it puts us on the cusp of an amazing revolution in our understanding. It will be fun to watch over the next few years. I’ve been following that Bittern that they’ve put a tracker on and even with just one bird the results have been fascinating.

Rohan: And one bird doesn’t make a major study, but often it’s enough to demonstrate that your belief system either reasonably good or really poor, and what this one bird is showing is that they’re probably broadly on line with what they’ve thought that Bitterns were doing, in that they are breeding in these rice paddies in what would have been the flood plains of the Murray-Darling basin then shifting to the coast, and making use of most of the sites that have been recognised as significant for Bitterns in Victoria and South Australia on the coastline, so this one bird has done this journey that has let us go tick, tick, tick, what we’ve thought about these birds is broadly OK even with a single sample.

Tony: Which presumably then provides us with a basis to ask more interesting questions, doesn’t it?

Rohan: Absolutely, it might better direct what you might do with more tags, so whether you target juveniles or adults, and at which stage of the movement you might target them.

Tony: Right. Well we might move along. I wonder if I could get you to run me through the current projects you are working on right at the moment.

Rohan: Sure. There are two big projects at the moment. One is in the north-west, of Australia, focussed on seabirds, looking at their movement ecology and foraging ecology of the Sulids, the Boobies, and Frigate Birds. That’s involving a whole suite of techniques and tools – basic capture methods, banding them, and usually taking a small blood sample and two or three individual feather samples at that time; and then a portion of those birds are also tracked, we’ve used a few different techniques.

Tony: Such as GPS trackers?

Rohan: Yeah. The feathers allow us to do stable isotope analyses, which give us insight into diet and trophic level, whether they’re top-order predators or whether they sit back a little from that; and what they have actually been consuming. The feathers are nice because, as with most birds, the seabirds are moulting in the non-breeding season so that gives us an insight into diet when they weren’t in the breeding colonies. With the blood we do pretty much the same analyses but we can go a little bit further by fractionating the blood and then doing the stable isotope analyses on the plasma and the red blood cells as two separate analyses. The plasma gives us an insight into what the bird has been eating over the last two weeks, because the plasma has a pretty high turnover; and then the red blood cells have slightly lower turnover so that gives us an insight into what the bird has been eating over the last month. That combination means that we’ve got insight into non-breeding season diet, and then very recently and a little bit further back as well. The main thing we’re looking for is changes in signal that allow us to infer that birds might be prey switching, both in the short to medium term but also between breeding and non-breeding seasons.

Tony: Sounds like a lot of work!

Rohan: (laughs). It is, yeah. The tracking side is the bit that is often the most exciting because you get an insight into what the birds have been doing – you know, what we’ve just been talking about – when we don’t necessarily have a good feel for that.

Tony: Very hard to do any other way, isn’t it?

Rohan: Yes. Rowan Mott is the PhD student who has been tracking the Frigate Birds, and we’ve got some quite astounding results there, in that we now know for Ashmore Reef and Adele Island, the frigate birds are doing from 3 to 8-10 day foraging trips when they’re on eggs or when they’re raising young, so one bird is left on the nest. We knew that timing from observation, but we didn’t know how far away they were going. From Ashmore they’re often going a thousand kilometres out into the Indian Ocean toward Indonesia and foraging out there, but they do these great series of big loop flights as well.

Tony: So they’re not really doing what they’re often advertised as doing, which is intercepting other seabirds coming back to shore and stealing their catch in flight?

Rohan: No, not at all. They only spend a tiny bit of time around the island before they do a long foraging trip. There was a little bit of evidence already that kleptoparasitism perhaps isn’t as important as previously thought but these tracking results also help to support that, in that most of their foraging is done away from focal areas where you might expect other engorged seabirds are likely to be aggregating – for example boobies coming back to the nest in the evening are an obvious target – and they don’t spend a lot of time in those areas.

The really cool stuff is that we put a bunch of Teflon harnesses on twenty Lesser Frigate Birds with GPS tags that are solar powered; and at the end of the breeding season almost all of those birds left Australian waters and wintered in the Java Sea. We’ve got 14 out of 20 back about six months later or thereabouts at the island when they downloaded their data when the next approached the base station. So we’ve now shown that these birds aren’t resident around the breeding islands, which is what’s often written about them, instead they have a very clear seasonal pattern and they move to a completely different area.

Tony: It completely changes our understanding of how they work, doesn’t it?

Rohan: Yes, absolutely. And once your understanding has changed, then it changes our understanding of the threat matrix, maybe they’re most threatened on the roosting islands in Indonesia rather than on the breeding islands in Australia – or vice versa, for that matter – it gives you another thing to think about in how you might go about managing these species that are remarkably long-lived. We’ve got one Lesser Frigate Bird from Ashmore that’s 21 or 23 years old, it was banded as a chick at Ashmore and we re-caught it as a breeding female two years ago. Insights like that also change the way you think about the birds – who does what, and how long they’re around for.

We have similar insight for all the Booby species as well. It’s a big project and when it all comes together over the next year or so its going to tell a really nice story.

Tony: Its quite a big undertaking to run a project at such a remote location.

Rohan: Yes, I guess we’ve been lucky and unfortunate at the same time, in that the main reason we had a platform of opportunity up there to do work was the Montara oil spill. We ran all the post-impact monitoring for the Montara oil spill and that meant we had vessels twice a year with excess berths that we could support PhD students on. We’ve also used Customs vessels; and we’ve also been really fortunate to be able to access the commercial birdwatching tours and use them as a platform at times as well, with really good support from them.

Tony: Fascinating! Moving on to the second project area…

Rohan: Yes. Avian malaria in the Torres Strait. We’re really interested in a few aspects of that system. One is just to get a much better understanding of bird movement through the Strait, so that’s coming from just being present there and keeping regular bird logs but also banding to work out who’s resident, so the birds that we re-trap in different seasons give us all that insight. If they’re banded as an adult in summer and then re-trapped in winter it starts pretty rapidly building up a picture of certainty around movement strategies for those species.

The avian malaria side involves screening for malaria and getting a good understanding of the system – what levels of prevalence we’ve got at a community level and what levels of prevalence we’ve got within individual species and how that all relates to whether you’re a migrant or a resident. Lee Peacock’s project is a significant part of that but is also very focussed on the health consequences of malaria infection in the field at an individual and at a species level. Surprisingly, this is something that hasn’t actually been looked at too much. There’s some classic examples such as the Hawaiian islands and the arrival of avian malaria there resulting in the loss of half their honeycreepers, but the fitness consequences of malaria in a wild bird community are rarely looked at, in part because its often seen as being just too hard, so that’s one of things were trying to tackle at the moment.

Tony: OK, we might wrap up by asking you for some general thoughts on where ornithological research is at in Australia at the moment, what some the challenges are that it’s facing and what some of the big questions are that maybe it needs to be addressing.

Rohan: At the broad level I think we’ve probably touched on some of the real challenges, such as getting a better understanding of how our birds are operating in a system that’s less predictable than a lot of other places around the world. We really do sit as a bit of an outlier to the Americas and Europe in terms of flyways and much more predictable systems with very clear-cut Springs and Autumns and things that you can set your clock by or mark off on your calendar with certainty. We just don’t have that.

We’ve been banding for a long time and we’ve got some remarkable insights from banding already but the technology is going to be the thing that really cracks that nut. I think Simon Griffith with some of his work on Zebra Finches really clearly shows how technology can completely change the way we think about things. We think about Zebra Finches as typically being highly promiscuous, short-lived, they bop in, they mate with anything, the produce babies, they move off somewhere else and track where it rains and do the whole thing again. They do the typical boom-bust cycle where they seek out the pockets of good resources based on rainfall. He’s used, I think PIT tags on zebbies to show that at least one site that is exposed to booms and busts, that they maintain strong pair bonds. They basically maintain that pair bond to the extent that they’re typically within a couple of metres of each other for most of their life except when one bird is incubating, and they do all of that right through bust periods as well. If the way tags have been used to do that research has changed the way we think about Zebra Finches, then the capacity to change the way we think about pretty all sorts of systems in field ornithology is coming soon I think.

A couple of other challenges are probably worth flagging. I think there is a real challenge at the grass roots level to maintain a core of banders that can train the next group of behavioural ecologists and field ecologists. In Victoria, with the loss of Charles and Joan Sandbrink, it just becomes harder and harder, and I don’t see that that’s necessarily going to improve. I wonder whether we need to think about other ways of training banders.

Tony: It is concerning. It’s very time consuming. While there are some quite vibrant banding groups around, certainly in Sydney and Canberra for example, I believe a lot of other places aren’t nearly as well served.

Rohan: I think it’s fair to say that Melbourne is one of those. Now in Victoria the only one that stands out to me is the shorebirds and the Victorian Wader Study Group, which is a fantastic way to cut your teeth but it doesn’t get you the mist netting experience you need if you’re working on the majority of Australian birds. I have had a couple of chats to David Drynan recently about intensive banding courses, knowing that they’ve been run in the past, and treating them not so much as a guaranteed opportunity to get your permit but treating them as an opportunity to get to a level were the workload associated with additional training should be greatly reduced.

Tony: Rohan, all of this discussion is set against a backdrop in ornithology that for me at least seems to have at least two major recent trends in it. The first is the recent revelations about Australia being the birthplace of the evolution of birds in general; the other being the revelations about alarming declines in a really wide range of birds, not just the Orange-bellied Parrots and Plains Wanderers and so forth, but even some of the quite commonplace birds where long-term declines in populations on the order of 50% are being observed for quite a few taxa now. How does that affect the whole equation, do you think?

Rohan: Hmmm, I don’t know. I feel a bit like it’s a bit of as running battle at the moment. Fortunately, in the bird world we haven’t lost that much at the species level; but gee, there’s an awful lot of things that are close, and there’s a lot more things that are close that weren’t that close a while ago. So it seems we’re pretty good at not letting species go extinct but were quite appalling at letting species become endangered. It seems we do a lot very late and we don’t do enough earlier in terms of improving things on the ground. Some of that probably just reflects our understanding of the system still and how we might go about improving that. For woodland birds at a really coarse level we need more habitat but what’s the best way of doing that to get the best result. We’re really only just chipping away at that now.

Tony: Yes, there’s been some really quite disturbing trends in the mallee in the South Australia – Victoria border area for example, driven by fire dynamics it seems.

Rohan: Absolutely. There’s some really big changes happening and these are very complex systems – ecology is never not complex! – so we’re juggling a baseline that is a typical boom-bust system anyway. Droughts are normal, pulse rainfall events are normal, fire is normal; and they’re just a few of the elements. Overall of that is habitat clearance and habitat loss, connectivity, metapopulation dynamics that are happening at decadal or even longer scales, so to understand them takes a long time.

Tony: Yes, I do wonder whether for a lot of these species what were actually just observing a steady repayment of the extinction debt that is already well in train and just takes a long time to work through, especially for long-lived Australian species.

Rohan: Yes, I think we are still paying extinction debt. I think regent Honeyeaters are a perfect example of that. There’s some threshold above which they seem to be able to bubble along reasonably well, presumably their rate of decline was reasonably slow but nevertheless they did decline, and once they got below that threshold the rate of decline really started to rumble along much more quickly than we would have expected from the earlier trajectory. Regent Honeyeaters are in trouble because of vegetation clearance that mostly occurred 50-60 years ago. They’re not particularly long lived, at least not when you’re thinking about individuals but when thinking about generational times, you can easily be pumping out a new generation every 2-3 years, so in that context its remarkable that they’ve hung on so long but then they’ve ended up in this dire situation without significant loss of vegetation in the last decade or two.

Tony: Maybe there’s other changes happening – noisy miners, cat and fox predation, who knows?

Rohan: Yep, then the millennium drought comes along and gives a little nudge in the direction it might all go if we get more extended series of these sorts of droughts in the future. But in the the millennium drought also sits as an example of the extremes that we expect in this continent even without climate change.

Tony: Indeed, and another trend that’s appearing, particularly in the inland districts, is this one that sees new records being set for long strings of 40+ or even 50+ days in summer.

Rohan: Yes, absolutely. And for a 6-8 gram mallee emu wren that doesn’t drink free water it’s hard to imagine how it manages in an extreme heat event that extends for 5 or 6 days. That sort of events could literally wipe them off the map for some areas. There’s solid evidence that it causes massive mortality for things like Budgerigars, so why wouldn’t it take out things like mallee emu wrens, it’s just that we wopuld never find them tucked away in the deepest darkest recesses of the spinifex clump when they pass away.

Tony: Rohan, that’s been most interesting and thank you very much for it.


*Hallworth M.T. & Marra P.P. (2015). Miniaturized GPS Tags Identify Non-breeding Territories of a Small Breeding Migratory Songbird.