This mission impossible was clearly not going to be a birdwatching exercise: many birdwatchers prize themselves in being able to spot over a hundred bird species in one day. The big birding day record stands at over 300 species spotted in a day. Our mission was a ringing exercise – but there are many catchers of birds who have caught well over this number of birds in a day too. So why was it a mission impossible?
First, we were targeting 12 species that included some of the rarest birds in the Fynbos. Before the commencement of the Fynbos Endemic Birds Survey in 2012, fewer than 30 Victorin's Warbler and Protea Seedeater had been captured in the entire history of bird ringing in South Africa. The only species where we could consider 'easy' were the nectar feeding Cape Sugarbird and Orange-breasted Sunbird as these species are both common and predictably found in areas with flowering protea and erica plant species. Many thousands of these have been caught over the history of ringing activities in South Africa. The little seed-eating Cape Siskins – well that one depended on the weather – it would be easy if it stayed dry, but they could disperse to anywhere in the inhospitable mountain terrain if not constrained by their need to drink water (as many seed eating species need to do). But bird ringing is never easy: the birds don't want to be caught after all.
Cape Rockjumpers had only been caught previously over ten years ago in a project dedicated to examining family structure in that species. In that exercise, only around 20 adult birds were caught, the rest of the birds were ringed as chicks in the nest. And for our exercise we needed 10 adult birds, preferably with an even mix of males and females. Furthermore, we could not process juvenile birds or female birds that were clearly in a breeding state (for example those with an active brood patch).
We also needed to compare the birds that live only in the Fynbos to birds that lived in a wider range of habitats that included the Fynbos. We thus had the six Fynbos endemic species paired with six non endemics that were comparable in terms of diet and size, but that we also knew we had a reasonable chance of catching. While these species are familiar to most South African birdwatchers: Familiar Chat, Cape Grassbird, Malachite Sunbird, Southern Double-collared Sunbird, Cape Canary and Cape Bunting, some of these species were to be a challenge since they are not reliant on the Fynbos and move out of it in order to exploit food resources elsewhere – a problem we would face especially with Malachite Sunbirds and Cape Canaries.
Second, we could only process a maximum of 3 birds a day. So Why and What do we mean by 'process'? Our project aimed to determine when birds start to feel the heat – technically speaking we wanted to know their upper thermal neutral zone and when they needed to start to expend energy in order to keep cool. Birds have to pant and flutter their wings in order to do this and these activities require energy. We needed to place the birds in an experimental chamber where we could control the air temperature. Air that the bird breathed out was then monitored for oxygen, carbon dioxide and water vapour content; and the temperature of the bird was monitored too. This would take around 3 hours per bird, and since the half million rands worth of equipment could only handle one bird at a time and the bird had to be monitored the entire time for signs of stress, this imposed an upper limit of how many birds we could 'process' at any one time.
So why did we want to do all of this? The short answer: Global Warming. Within scientific realms there is no doubt that climate change is real and that combustion of carbon-based fuels are the cause of recent rapid increases in temperature (together with changes in rainfall regimes, melting of the icecaps and increases in sea level). During 2012, a modelling exercise of where the Fynbos birds occurred suggested that at least two of the species were selecting areas that were cooler than the rest of the Fynbos, a biome that is the coolest of the southern African broad habitat types, due to its location (restricted to the southern tip of the continent) and topography (located almost entirely around the Cape Fold Mountains much Fynbos is at high elevation, which tends to be cooler). Global warming predicts that a species will need to shift towards the poles or upwards in elevation in order for that species to stay in the temperature zone that it likes. However, Fynbos has nowhere to go – it is already as south and up as you can get in Africa - and so is especially vulnerable to climate change.
However, modelling that a species is vulnerable to climate change is not proof that a species is vulnerable to warmer temperatures. There may be other aspects of a species' lifestyle that determine why it lives where it does. There are also many ways a species can use its environment to avoid extreme temperatures. For these reasons, we needed to test how the Fynbos species were physiologically able to deal with high temperatures.
That is the background to our mission impossible. Here is how the mission unfolded.
After analysing results from a survey of birds from across the biome and realising they were vulnerable either directly or indirectly to climate change, I had earlier in the year mentioned to Dr Susie Cunningham at the Fitz of the need to conduct a project to examine specific vulnerability to heat. Susie is a member of Andrew McKechnie's Hot Birds program which aims to examine the impact of climate change on birds, with a focus specifically on hot and arid environments. A few months later Robyn Milne, a Conservation Biology Masters student at the Fitz, approached Susie for a physiology based practical project. Susie had worked closely with Ben Smit, who was just finishing his PhD (supervised by Andrew) looking at precisely what we needed to examine for the Fynbos suite of birds, and had access to all the necessary lab equipment through his new lectureship post at Nelsom Mandela Metropolitan University (Port Elizabeth). Susie had thus assembled the definitive team that would be able to show once and for all whether our concerns were justified.
We also needed a study site where all the Fynbos endemic bird species occurred in reasonable numbers – and Blue Hill Nature Reserve seemed to be ideal. Adjoining the south-western section of the Baviaanskloof Nature Reserve, this small nature reserve (2300ha) consists mostly of mountain Fynbos, interfacing with arid Karoo. All the endemics, and critically those identified as vulnerable to climate change – Protea Seedeater and Cape Rockjumper – had all been ringed or seen here before.
The project's first hurdle would be convincing the University of Cape Town's ethical committee that we would not be roasting live birds to death, which was often the joke response by anyone we were describing the project to. We had to assure the committee we would be doing everything in our power to care for the birds we were using for this study, that they would be well looked after, fed and monitored throughout their time in temporary captivity. By way of a comparison with humans, what we were doing is the equivalent of seeing when the birds would 'break a sweat' and then seeing at what rate they would sweat. Technically, this is looking at when the birds start to pant and how fast they loose water vapour. After several months of discussion, clarification and thought we were given ethical clearance and by the end of the project no birds were lost while in the experimental chambers. We had recaptures or re-sightings in the field of individuals that had been processed several days after they had been released, suggesting that those that had 'volunteered' their time had recovered from the ordeal.
The team (Robyn, Susie and Ben) arrived at Blue Hill Nature Reserve on 22 September. Robyn and Ben (with the help of Ben's recently betrothed) had the myriad of pipes, tubes, pumps, heaters, air monitoring equipment, video screens and specialized software set up by the Monday evening. I was shocked – up till that point I had been under the impression that all we were dealing with was a glorified cooler box that we could transport up to where we were catching the birds. The delicate equipment needed a lot of electric power and occupied several square meters of space. Since we don't happen to have 120 target species living just outside the house, this meant that in addition to catching our target species, we would also have to transport them from ringing locations back to the lab and return them to their original locations.
Blue Hill Nature Reserve is not a game reserve with the paved road infrastructure that you may imagine of Kruger National Park – it's a corner of what was once known as the Baviaanskloof Wilderness Area. Infrastructure over the rocky terrain is by 4x4 only – and its takes about an hour to get from the lodge area up to the mountain tops (Cape Rockjumper territory) even though the distance is less than 10km by rocky track. On the very first day of testing out a quad-bike's ability to deal with the terrain we'd blown the water pump. The solution again would be climate friendly – the fastest way off the mountain would prove to be by mountain bike, with the bird carried in a specially constructed shock-proof container. However, it did mean that our days would be very long – typically starting around 4am and finishing at 6pm when the last of the birds had been returned to the site where it had initially been captured.
Our first day out would be a site not far from Blue Hill Escape in an area of mature Protea dominated Fynbos. I was a bit concerned that when the main protea species ended its flowering season that the Sugarbirds would soon be heading over the mountain to inaccessible sites. However, the first target bird we caught was a Cape Grassbird. This species was our comparison species for the endemic Victorin's Warbler, and up until that time of the 3000 odd birds I had caught at Blue Hill Nature Reserve, only 20 had been Cape Grassbirds. It was decided that this would be the first bird to be processed by Ben and Robyn back at the lab, and all went well. Two Cape Sugarbirds from that site were captured the next day, after which we were sure our methods were working.
Since Ben and Susie could only stay for a short period, it made sense to target the most remote sites first, before I had to take charge of all ringing by myself. We split into two teams: Ben would operate a netting team close to the house at a seep where many small birds were coming to drink; while Susie and I headed for the furthest section of the reserve. This mountain top site has beautiful views of all the surrounding Cape Fold Mountains – Tsitsikamma to the south, Baviaans to the East, Kammanassie to the west, and Swartberg to the north. Here a month earlier I had seen six Cape Rockjumpers displaying to the backdrop of cloud topped mountains. We set out 100meters of net across the rocky terrain. After four hours the wind was up, and the nets had not caught a single bird, perhaps not a surprise as the barren landscape offered few sites to conceal the nets, which on the mountain top also became quickly visible due to sun and wind.
We also placed 10 baited traps on boulder outcrops. The modus operandi for the baited traps was slightly different. A baited trap (or snap trap as we preferred to call them) is a spring loaded trap that throws a net over the bird that takes the wriggling mealworm bait. These were placed out at regular intervals on flat rocks in a line that could be easily observed from a distance, or that could be easily found on a regular patrol. After a few days it was clear this method would work and the nets were abandoned on the second day with still not a single bird caught. Our first bird caught in the snap traps was a Sentinel Rock-Thrush, the first ever for the Western Cape. At this stage we were still not sure what species would be a good match for the Cape Rockjumper, and so we decided we would try the Sentinel Rock-Thrush.
This would be the first bird that would be transported off the mountain by mountain bike. The rocky trip off the mountain took 45 minutes, shaving half an hour off the time it had taken to get us up the mountain in a Toyota Landcruiser. On reaching Ben's netting location I would normally have been overjoyed by the news that Susie in the meantime had bagged our first Cape Rockjumper, but for me this meant a cycle back up the mountain to retrieve it – a journey that would take double the time of the descent as certain steep gravel sections of the track had to be walked. While I had been making my descent with the Rock-Thrush, Susie had repositioned the traps to a location where a pair of Rockjumpers had been spotted. A male bird had taken the bait while she was still setting the last of the traps. Over the next few days with a careful combination of identifying territories, watching the birds to find preferred forage sites, setting traps and then lots and lots of patience, a Cape Rockjumper was caught on almost every day. This doesn't mean it was easy – on one day we were watching birds through flurries of snowflakes. Teamwork was an essential part of the mix, with much use made of a pair of walkie-talkies loaned to us by Ross Wanless of BirdlifeSA.
Ben had been having similar success at the seep near the lodge, resulting in the capture of the project's first Protea Seedeater as well as numerous Cape Siskins. Unlike the rest of the Western Cape, which had experienced good winter rainfall, the eastern sections of the Klein Karoo had been rather dry. This meant a lot of thirsty birds were seeking out water sources wherever they remained, all the more so as the frosty mornings of the first few weeks gave way to clear days with scorching temperatures. Later on in the project we would measure temperatures close to 50 degrees in the sun – part of an experiment to see what temperatures the birds may well be experiencing in exposed positions in the landscape.
After Ben and Susies departure back to the halls of academia, it was just Robyn and myself tasked with catching more birds. The target for this period was the elusive Victorin's Warbler. We cut dedicated netting lanes and erected many meters of net through protea covered hillsides in areas where we heard pairs calling. Only one bird would ever be caught without the aid of playback of the species call – they are very net aware, not a surprise for a species that navigates its way through the Fynbos undergrowth. It also became very clear that it was next to impossible to catch birds that had been caught previously. The birds would approach the netting lanes, and then move along them until they found a way around or under. Even attempts to flush them into the net met with only partial success.
By the end of two weeks Robyn and I had worked ourselves ragged. Sniffing and coughing we were delighted by the arrival of Craig Kenny. Craig had enlisted on the Blue Hill volunteer program as part of a round the world adventure – little did he know how much adventure was in store for him. On only his second day out with us we encountered a Cape Mountain Leopard watching us from a steep crag. It was later re-sighted hunting dassies. But it was great to have an extra pair of (humna) eyes to watch the traps (we had not caught any more Rockjumpers since Susie's departure) and to ferry birds to the lab and then back to the field, biking and hiking all day long. On several days Craig and I headed off at 2:30 in the morning in order to get to a remote valley to attempt to catch more Victorin's Warblers. Craig also helped me dig out and replace faulty electric cables that were seriously hampering Robyn's work processing the birds we had captured and had us running the house electric off a generator for several days. At the end of his four week stay with us he was so tough he was able to stand off a mugging attempt by four men on the outskirts of George, making headlines in the George Herald newspaper.
The biggest barrier to catching birds must be the weather, and sunny conditions with howling winds left us empty handed and frustrated on several occasions. Each evening we would tune into Norwegian weather website yr.no in order to plan the next day's foray – was it snap-trap only weather? But not even snap traps would work if placed on a windward slope. Towards the end of October we also saw the end of the dry winter. While the first few days of rain were a welcome excuse to stay in bed and not battle 4x4 trails while bleary eyed in the dark, after several days frustration would set in. On one weekend we were resigned to several days of data entry and analysis as rain poured down outside. The cloud burst resulted in a log jam on the entrance road to the reserve that I had to spend one afternoon clearing, while I would much preferred to have been sleeping. Pulling logs out of the river crossing resulted in a back spasm that left me almost immobile on one morning – but it was the day we caught our tenth and last Cape Rockjumper, so the celebrations overshadowed the pain.
There were several other capture highlights too. On one morning we arrived at our ringing location with new volunteer from France, Pauline. The north-wester was already rocking the net poles at the location we'd staked out the previous afternoon. A last minute snap-decision was made to head to Rockjumper territory on the other side of the mountain and so at 4.30am we found ourselves navigating a boulder strewn hillside by moonlight as mist blew over the mountains around us. The scenery was so unreal it was as though we were walking over the surface of the moon itself. On another day we'd set out 100 meters of net, missed the target Grassbird, but netted two other target species instead. As I sat with Pauline repairing damaged nets at the end of the session a pair of Protea Seedeaters flew in and perched in the bushes behind us. “We need those!” I said to Pauline and as if they'd heard me one promptly flew into the net over my head.
At another unsuccessful Grassbird location I went for a walk to an adjacent valley scouting for more possible Victorin's Warbler territories. I heard a Protea Seedeater and had my recording equipment with me. I recorded the bird's call, played it back and it flew out of the valley, perching close to me looking for an intruding doppelgänger. I then lured the bird using his own voice all the way to the other side of the mountain and into the net, a distance of several hundred meters.
The two species that we failed to achieve enough captures for were Malachite Sunbird and Cape Canary. The Malachite Sunbird was the big surprise – only a few months earlier I'd been catching twenty a day, and when the team had arrived there were plenty on flowering Sutherlandia bushes. In fact, we caught several early on in the field season, but always let them go to process the priority endemic bird species instead, thinking we would catch more at any stage. And then they disappeared. The Sutherlandias had stopped flowering and they headed over the mountain to flowering Leonotis stands in the Langkloof much too far away for us to visit. The Malachites that remained were all resident birds that had been caught before and avoided the nets adeptly. On one occasion I watched a splendid green male fly up to a monofilament net, a net early invisible even to the human eye, hovering along it and fly around the side. That was when I knew we were defeated. The Cape Canaries put in a similar disappearing act when the rains arrived.
By the end of the 60 days of ringing, November 2013, we had caught 593 individuals of 47 species, including 393 of our target 12. The datasets for the most important group – the Fynbos endemic bird species- were near complete. Robyn spent the next few months agonising over statistics and writing up, culminating in a degree with distinction. Her analyses showed that these (and specifically the Protea Seedeater and Cape Rockjumper) had much lower temperature thresholds compared to various bird species that Ben had examined from the Kalahari. So while the mission was impossible, at least we achieved enough that we could call it a success. The conclusion: the Fynbos Birds are not physiologically suited to warmer temperatures and will be at an ecological disadvantage due to temperature increases associated with Climate Change.
The project would not have been possible without the help and support of many people: Anja Kirchdrfer Lee ensured we were never hungry and fed well at the end of each long day; Peter Ryan and the FitzPatrick Institute at the University of Cape Town facilitated and funded much of the project; Maxine Smit helped with the setup of the equipment; Chris Lee provided the Toyota Landcruiser and subsidized much of the fuel costs; and an NRF grant to Phoebe Barnard facilitated Alan Lee's participation in the project.
|Bogey bird - Cape Canary|
|Cape Rockjumper, female|
|Cape Rockjumper, male|
|Young Cape Sugarbird to the lurid background of Susie's fleece|
|Caught on Camera: Didn't feel like I was speeding! On the way to return a bird to capture site.|
|Pauline: Sometimes its easier just to push|
|First Cape Rockjumper, a big moment.|
|Robyn, Craig and Elena in the lab|
|Cape Rockjumper in the respirometery chamber|
|Bogey Bird number 2: Malachite Sunbird|
|Southern Double-collared Sunbird, our control species for the Orange-breasted Sunbird, on a Sutherlandia (Lessertia)|