​In a recent blog post I mentioned the research of the Hot Birds Project and the new research into how pied babblers respond to high temperatures that is going on. Amazingly, a new paper which is really relevant to that sort of work has just come out in Science. This research, by Mariette and Buchanan looks at acoustic communication between parents and their offspring in birds. This isn’t the normal adult bird chirping to a chick but communicating to their unhatched offspring. Zebra finches acoustically signal high ambient temperatures (>26°C) to their unhatched embryos, resulting in developmental changes to the offspring. This is brought about solely by using acoustic cues. This type of work is especially exciting because it shows potential coping mechanisms that animals may have for changing climates, it is also an exciting meeting point of parental effects, phenotypic plasticity and climate science. I’ve put the abstract and link to the article at the end of the post.

Link to video to help explain the 'talking to their eggs when hot' paper: http://www.sciencemag.org/news/2016/08/video-zebra-finch-call-prepares-their-eggs-climate-change?utm_source=newsfromscience&utm_medium=facebook-text&utm_campaign=zebrafinch-6739

The other cool paper that has come out recently is work looking at Atlantic canaries and inbreeding. Males who were inbred were worse at singing and females mated less often with inbred males, producing fewer eggs. So for canaries it seems that singing is a honest signal of male genetic quality, adding credence to the ‘good genes’ hypothesis – the idea that male signals are a true representation of their genetic quality and females choose mates for this reason. Work on lizards, mice and lemurs have shown that olfactory cues are linked to genes related to immunity. I love this kind of science, I find it so fascinating. It also has impacts for helping to understand conservation issues with species range and population sizes and how to ensure viable populations. Again, the abstract and link are below.

Mariette & Buchanan (2016) Prenatal acoustic communication programs offspring for high posthatching temperatures in a songbird. Science, 353:812-814
In many species, embryos can perceive and learn external sounds. Yet, the possibility that parents may use these embryonic capacities to alter their offspring’s developmental trajectories has not been considered. Here, we demonstrate that zebra finch parents acoustically signal high ambient temperatures (above 26°C) to their embryos. We show that exposure of embryos to these acoustic cues alone adaptively alters subsequent nestling begging and growth in response to nest temperature and influences individuals’ reproductive success and thermal preferences as adults. These findings have implications for our understanding of maternal effects, phenotypic plasticity, developmental programming, and the adaptation of endothermic species to a warming world.

De Boer et al. (2016) ‘Out of tune’: consequences of inbreeding on bird song. Proc Roy Soc B
The expression of bird song is expected to signal male quality to females. ‘Quality’ is determined by genetic and environmental factors, but, surprisingly, there is very limited evidence if and how genetic aspects of male quality are reflected in song. Here, we manipulated the genetic make-up of canaries (Serinus canaria) via inbreeding, and studied its effects upon song output, complexity, phonetics and, for the first time, song learning. To this end, we created weight-matched inbred and outbred pairs of male fledglings, which were subsequently exposed to the same tutor male during song learning. Inbreeding strongly affected syllable phonetics, but there were little or no effects on other song features. Nonetheless, females discriminated among inbred and outbred males, as they produced heavier clutches when mated with an outbred male. Our study highlights the importance of song phonetics, which has hitherto often been overlooked.

I’ve just returned from a fun but fairly hectic trip to the Kalahari. This chance came about because there is a new PhD student starting on the pied babblers but no one was available to train her. So, on a plane I hopped and met up with Amanda Bourne. She’s going to be looking at climate effects on the babblers and be part of the Hot Birds Project. Her work is going to be a mix of: physiology, trying to understand the metabolic costs; behavioural, working out if temperature impacts on social and group cohesive behaviours – trying to see if sociality may act as a buffer to high temperatures; and investigating cumulative impacts of high temperature on groups and individuals. All this is really cool, interesting, and (pardon the pun) hot stuff. She is following on from other hot birds work at the Kuruman River Reserve: van de Ven et al. 2016 found that hornbills can regulate blood flow to their beaks to regulate their temperature without evaporative heat loss; du Plessis et al. 2012 found that increasing temperature caused a decrease in the foraging success of pied babblers, with birds displaying heat dissipation behaviour while foraging. She’ll also be able to build on some recent babbler work by Lizzie Wiley who found that adults provisioned nestlings much less on hot days, resulting in decreased nestling growth (Wiley & Ridley 2016).
 
So why was I there? Well the babblers are a bird with lots of complex behaviours, fairly defined territories and the project has specific protocols to maintain consistent data collection over its 13 year history. The privilege fell to me to basically walk around and look at birds for 10 days solid, life is so hard! But in all seriousness, the study population consists of wild birds who have been habituated to close human presence and without knowing how to act around them it is possible to dehabituate them very quickly and see your PhD data quickly fly away. I was also able to help Amanda figure out potential research questions and experiments that she wouldn’t have been able to think of without seeing how they behave.
 
Before heading off I was anticipating a fairly dull period in the field: its winter, they’re hungry and so they just forage and fly about between the distant patches of low density prey. How wrong I was. This has been a very odd year in the Kalahari, late summer rain in April and a mild winter led to a bumper abundance of food. When food is not a problem the babblers, and all of the other Kalahari animals for that matter, get it on and babies are the result. We arrived to find multiple groups with fledglings, and so the veldt was alive with the begging of babblers – music to my ears. Following these groups of babblers where the scimitar bills taking advantage of babbler sentinels and the ubiquitous drongos. We found groups like Centaurus (pictured below) incubating and even observed some egg eating in a group with females who were competing for reproduction. Whilst other groups were having large aerial battles with their neighbours. Amanda was privileged to observe a dispersal event, the dominant female of Vivaldi was fed up with her light weight male and decided to fly across to join the much heavier male of neighbouring group Noleg, even though at one point she flew back to join her old group for a fight against another group before quickly remembering that she’d left.
 
Whilst looking for groups, and teaching Amanda the babbler whistle (an ululating call to get the birds to fly to you) and group territories, we came across wild groups and individuals who had dispersed from the study population (one may have last been seen in the population in 2004!! – although confirmation is still needed). One of these wild groups was right in the middle of the reserve and feeding a nest, so they’ve been named (Martu- pronounced Mardu – after the aboriginal people of the Western Deserts of Australia) and habituation may start in September when Amanda gets back. 

Amanda’s boyfriend, plant biologist and restoration ecologist extraordinaire, Todd Erickson also came along. He was able to use my camera a lot more than I was, and many of the pictures on the blog post were taken by him. Todd’s botanical leanings allowed me to see the veldt in a new way, paying attention to the small succulents, grasses and flowers that had flourished because of the late rains. The Kalahari was filled with colour, majestic in its flora. This colour had been included in the babbler nests, with many of them decorated with the lovely yellow flowers that littered the landscape. Todd’s insights about how dunes actually hold water better than the slacks, meaning that larger trees and shrubs can grow there, blew my mind and made me look at the landscape in a completely new way. This is why I love science, there are so many disciplines and you can always learn something new that changes your world view.
 
I’ve written mostly about the babblers, and that’s because they are awesome, but there are many other projects at the KRR. There is the over 20 year study of meerkats, who have had a terrible year: prior to the late rains it had been a drought and their groups had been decimated by the combined disasters of no recruitment and TB, but they had started to breed in the winter. The Cape Ground Squirrel Project, started by my friend Jamie Samson, is still going strong and again they have had loads of strange winter pups. And for those of you who want to fly to South Africa, travel for hours to the remote Kalahari and then spend most of your time indoors there are always the molerats to work on. That might sound a bit negative but I like being outside and observing animals behaving in their natural habitat and the idea of spending all day under florescent lights (something you can do in an office) in a building that smells of pee (something you get in public toilets) isn’t something that appeals to me. The other cool birds that are studied at the KRR are the hornbills (mentioned above) and the drongos – who spend their time either stealing food from other animals with their vocal mimicry, catching flying insects with ease using their aerial acrobatics or just pissing off large raptors by bomb diving them.

It was very special to go back to the Kalahari, a place that I have spent a lot of time. Seeing the babblers again, watching them play in shepherd’s trees, feed their fledglings or just have them hop on my feet as I weighed them was very special. I also found out that part of my hippocampus is forever engraved with a map of the reserve: I could still walk straight to ladders hidden behind bushes, find trees that had been used as nests in the past and always point to Whiskers Crossing. Part of me will always be in the Kalahari, and no view will ever be as beautiful as the sun setting over the dunes or a time as peaceful as dawn in the veldt.

In the spirit of many of my previous blogs I am going to write about a new paper written by someone I know. This may sound like some sort of nepotism, not that many people really read my blog, but this new paper has actually made quite a splash and so I’m really just following a great new science story. If you want to see some of the other coverage then click on these links: Science, Sci News, Science Daily, or PLoS Blogs. (The abstract and link to the paper in question is at the bottom of the blog)
 
This new piece of research is a product of the Hot Birds team at the Fitz in Cape Town, with Tanja van de Ven (lead author) spending many gruelling hours in the Kalahari heat with fairly complex equipment. The team, and Tanja’s, aim is to investigate how birds cope with rising temperatures using species that already exist in the hard thermal conditions of the Kalahari. One of their papers looked at the impact of heat stress on foraging in pied babblers. However, Tanja’s work focuses on yellow-billed hornbills, a species of bird that nests inside trees, with the female sealing herself into this cavity. This reproductive adaptation is great for protecting your eggs and female from predators but it can limit your ability to control your temperature, as you’re pretty stuck (it also means that the female and chicks are 100% dependent on the male for their nutritional needs – such a cool system for male-female and parent-offspring dynamics!!!).
 
The obvious feature of this bird, hopefully you have either clicked on the link or already know what a hornbill looks like from your bird knowledge or from childhood exposure to the Lion King, is that they have a massive long bill. The beak of a bird is not just lifeless tissue like finger nails but very much a living structure and as such has a profusion of blood vessels. Just like the thermoregulation that takes place in humans, where capillaries close to the surface are constricted or relaxed to either conserve or radiate heat, hornbills appear to have the same ability with the blood vessels in their beak. As the ambient air temperature increases more blood is pushed into the hornbill’s beak, allowing heat to be lost through radiative heat transfer. This is similar to toucans, as a recent study has found, but in the toucan this process accounts for upto 60% of non-evaporative heat loss compared to just 8% in the hornbill. There are a number of potential reasons for this: the toucans have much larger bills, hornbills have a harder bill (maybe an ecological adaptation to how they forage?) and toucans start dilating their blood vessels at lower temperatures.
 
This type of research is crucial for understanding how organisms are physiologically adapted to their environment. It enables researchers to better understand the environmental limits that a species may be able to cope with and allow predictions as to the impacts of climate change. It’s also pretty cool too.
 
 
van de Ven et al. (2016) Regulation of heat exchange across the hornbill beak: functional similarities with Toucans? PLoS One
 
Beaks are increasingly recognised as important contributors to avian thermoregulation. Several studies supporting Allen’s rule demonstrate how beak size is under strong selection related to latitude and/or air temperature (Ta). Moreover, active regulation of heat transfer from the beak has recently been demonstrated in a toucan (Ramphastos toco, Ramphastidae), with the large beak acting as an important contributor to heat dissipation. We hypothesised that hornbills (Bucerotidae) likewise use their large beaks for non-evaporative heat dissipation, and used thermal imaging to quantify heat exchange over a range of air temperatures in eighteen desert-living Southern Yellow-billed Hornbills (Tockus leucomelas). We found that hornbills dissipate heat via the beak at air temperatures between 30.7°C and 41.4°C. The difference between beak surface and environmental temperatures abruptly increased when air temperature was within ~10°C below body temperature, indicating active regulation of heat loss. Maximum observed heat loss via the beak was 19.9% of total non-evaporative heat loss across the body surface. Heat loss per unit surface area via the beak more than doubled at Ta > 30.7°C compared to Ta < 30.7°C and at its peak dissipated 25.1 W m-2. Maximum heat flux rate across the beak of toucans under comparable convective conditions was calculated to be as high as 61.4 W m-2. The threshold air temperature at which toucans vasodilated their beak was lower than that of the hornbills, and thus had a larger potential for heat loss at lower air temperatures. Respiratory cooling (panting) thresholds were also lower in toucans compared to hornbills. Both beak vasodilation and panting threshold temperatures are potentially explained by differences in acclimation to environmental conditions and in the efficiency of evaporative cooling under differing environmental conditions. We speculate that non-evaporative heat dissipation may be a particularly important mechanism for animals inhabiting humid regions, such as toucans, and less critical for animals residing in more arid conditions, such as Southern Yellow-billed Hornbills. Alternatively, differences in beak morphology and hardness enforced by different diets may affect the capacity of birds to use the beak for non-evaporative heat loss.

A recent bit of research has just come out that shows that bird populations in Europe and the US are being impacted by our changing climate. This work was even picked up by the BBC. By using a combination of great long-term datasets and some nifty models that they created, the researchers were able to predict current population distributions. This is not just well done research but also a testament to the importance of long-term population monitoring, something that isn’t sexy and since the financial crisis hasn’t received as much funding as other more applied areas of science (sorry this is a pet peeve of mine and I’ll get off this tall equid that I now find myself on). What the research has shown is that species that are predicted to benefit from climate change are benefiting, and those that are predicted to suffer are suffering. Both positive and negative effects can occur within a single species, as they may be declining in southern regions but thriving in northern areas.
 
The trends shown by this new research are large scale continental patterns but what factors may be driving these at a finer, individual level scale? Work done by researchers like Susie Cunningham, Rowman Martin and my pied babbler colleague Lizzie Willey is shedding light on this. Work by these researchers, and others, has shown that when temperature increases it can have dramatic effects on the reproduction of birds, their ability to forage and the viability of their social groups. Nestling fiscal shrikes grow slower when temperatures increase over a threshold level: this increases the risk of nest failure and results in smaller fledglings who are likely to incur a fitness cost. Similarly, on warmer days pied babblers are less efficient at foraging and put on less weight while foraging. If multiple extremely hot days occur in a row this could have a dramatic impact on an individual’s weight, and if they are caring for young then temperature will impact adults, offspring or both. Anecdotal evidence, hopefully soon to be verified statistically, of pied babbler groups is that in the hottest years more groups fail to raise any offspring and become extinct, presumably from the direct effects mentioned above. All of these small individual level mechanisms may help to understand the drivers behind higher level continent wide patters.
 
But climate change doesn’t just act on its own, it occurs in conjunction with direct habitat change caused by humans. Pied crows in South Africa have changed the areas in which they live based on a change in climate but it is facilitated by power lines. These birds need to nest in trees and the existence of power lines has allowed them to colonise treeless areas and take advantage of them.
 
But what does all of this mean? By understanding the lower level effects it may be possible to design or implement habitat measures that can mitigate some of these effects. This may be farfetched, as these are large scale problems. For example when putting up nest boxes for endangered species it is important to ensure that they are not going ‘cook’ the nestlings inside, it’s worth spending that extra time researching this before spending large sums of money on a conservation effort that is doomed to fail. Small and simple considerations like that may have an impact.
 
For more information on this type of research you can visit the Hot Birds Research Project.
 
Some papers that look at the direct effects:

Cunningham et al. (2013) Temperatures in Excess of Critical Thresholds Threaten Nestling Growth and Survival in A Rapidly-Warming Arid Savanna: A Study of Common Fiscals. PLoS ONE
Frequency, duration, and intensity of hot-weather events are all predicted to increase with climate warming. Despite this, mechanisms by which temperature increases affect individual fitness and drive population-level changes are poorly understood. We investigated the link between daily maximum air temperature (tmax) and breeding success of Kalahari common fiscals (Lanius collaris) in terms of the daily effect on nestling body-mass gain, and the cumulative effect on size and age of fledglings. High tmax reduced mass gain of younger, but not older nestlings and average nestling-period tmax did not affect fledgling size. Instead, the frequency with which tmax exceeded critical thresholds (tcrits) significantly reduced fledging body mass (tcrit = 33°C) and tarsus length (tcrit = 37°C), as well as delaying fledging (tcrit = 35°C). Nest failure risk was 4.2% per day therefore delays reduced fledging probability. Smaller size at fledging often correlates with reduced lifetime fitness and might also underlie documented adult body-size reductions in desert birds in relation to climate warming. Temperature thresholds above which organisms incur fitness costs are probably common, as physiological responses to temperature are non-linear. Understanding the shape of the relationship between temperature and fitness has implications for our ability to predict species’ responses to climate change.

Cunningham et al. (2013) Identifying Biologically Meaningful Hot-Weather Events Using Threshold Temperatures That Affect Life-History. PLoS ONE
Increases in the frequency, duration and intensity of heat waves are frequently evoked in climate change predictions. However, there is no universal definition of a heat wave. Recent, intense hot weather events have caused mass mortalities of birds, bats and even humans, making the definition and prediction of heat wave events that have the potential to impact populations of different species an urgent priority. One possible technique for defining biologically meaningful heat waves is to use threshold temperatures (Tthresh) above which known fitness costs are incurred by species of interest. We set out to test the utility of this technique using Tthresh values that, when exceeded, affect aspects of the fitness of two focal southern African bird species: the southern pied babbler Turdiodes bicolor (Tthresh = 35.5°C) and the common fiscal Lanius collaris (Tthresh = 33°C). We used these Tthresh values to analyse trends in the frequency, duration and intensity of heat waves of magnitude relevant to the focal species, as well as the annual number of hot days (maximum air temperature > Tthresh), in north-western South Africa between 1961 and 2010. Using this technique, we were able to show that, while all heat wave indices increased during the study period, most rapid increases for both species were in the annual number of hot days and in the maximum intensity (and therefore intensity variance) of biologically meaningful heat waves. Importantly, we also showed that warming trends were not uniform across the study area and that geographical patterns in warming allowed both areas of high risk and potential climate refugia to be identified. We discuss the implications of the trends we found for our focal species, and the utility of the Tthresh technique as a conservation tool.

Cunninham et al. (2016) Electric crows: powerlines, climate change and the emergence of a native invader. Diversity and Distribution
Aim
Climate change and other anthropogenic global change drivers act in complex, mutually exacerbating ways to alter the abundance and distribution of species. In South Africa, pied crowsCorvus albus have increased in numbers and range in recent decades. Popular opinion links these changes to urbanisation and infrastructure development, but there has been no empirical test of this idea. We aimed to clarify the drivers of pied crow population changes in South Africa.
Location
South Africa.
Methods
We used publicly available long-term datasets, the Southern African Bird Atlas Project and University of Delaware Gridded Climate Database, and spatial data from government bodies, to assess relationships between pied crow population and range changes, land use, infrastructure, urbanisation and climate change.
Results
Pied crow numbers have increased significantly in the past three decades, but rate of increase varied geographically, with crows declining in the northeast and increasing in the south-west of South Africa. Pied crow population changes were strongly correlated with climate change. Crows have benefited most from climate warming in the shrubland biomes of south-western South Africa. Pied crows are tree nesters, and within these shrublands, there is a strong positive relationship between the rate of population increase and the density of powerline infrastructure, which may facilitate pied crows’ increase by providing nesting sites.
Main conclusions
Pied crow numbers have increased in response to climate warming, with their spread facilitated by electrical infrastructure in south-western South Africa, providing a clear example of compound influence of multiple global change drivers promoting a significant change in species range and reporting rate. Pied crows are generalist predators and there is popular concern about their ecological impact in areas where increases have occurred. We highlight the importance of understanding the ecosystem-level implications of increased numbers of pied crows in South Africa's shrubland biomes.

Du Plessis et al. (2012) The costs of keeping cool in a warming world: implications of high temperatures for foraging, thermoregulation and body condition of an arid-zone bird. Global Change Biology
Recent mass mortalities of bats, birds and even humans highlight the substantial threats that rising global temperatures pose for endotherms. Although less dramatic, sublethal fitness costs of high temperatures may be considerable and result in changing population demographics. Endothermic animals exposed to high environmental temperatures can adjust their behaviour (e.g. reducing activity) or physiology (e.g. elevating rates of evaporative water loss) to maintain body temperatures within tolerable limits. The fitness consequences of these adjustments, in terms of the ability to balance water and energy budgets and therefore maintain body condition, are poorly known. We investigated the effects of daily maximum temperature on foraging and thermoregulatory behaviour as well as maintenance of body condition in a wild, habituated population of Southern Pied Babblers Turdoides bicolor. These birds inhabit a hot, arid area of southern Africa where they commonly experience environmental temperatures exceeding optimal body temperatures. Repeated measurements of individual behaviour and body mass were taken across days varying in maximum air temperature. Contrary to expectations, foraging effort was unaffected by daily maximum temperature. Foraging efficiency, however, was lower on hotter days and this was reflected in a drop in body mass on hotter days. When maximum air temperatures exceeded 35.5 °C, individuals no longer gained sufficient weight to counter typical overnight weight loss. This reduction in foraging efficiency is likely driven, in part, by a trade-off with the need to engage in heat-dissipation behaviours. When we controlled for temperature, individuals that actively dissipated heat while continuing to forage experienced a dramatic decrease in their foraging efficiency. This study demonstrates the value of investigations of temperature-dependent behaviour in the context of impacts on body condition, and suggests that increasingly high temperatures will have negative implications for the fitness of these arid-zone birds.

A great new piece of research has just been published by some of my old colleagues at the Fitz in Cape Town (Susie Cunningham and Arjun Amar). It’s work that I help with at its inception, and it shows that pied crows have changed their distribution in South Africa and it’s mainly due to changes in climate and the distribution in power lines. A great piece of research that shows how the twin human impacts of climate change and habitat modification are shaping the natural world.
 
Cunningham et al. (2015) Electric crows: powerlines, climate change and the emergence of a native invader. Diversity and Distributions, DOI: 10.1111/ddi.12381
 
Abstract
Aim
Climate change and other anthropogenic global change drivers act in complex, mutually exacerbating ways to alter the abundance and distribution of species. In South Africa, pied crows Corvus albus have increased in numbers and range in recent decades. Popular opinion links these changes to urbanisation and infrastructure development, but there has been no empirical test of this idea. We aimed to clarify the drivers of pied crow population changes in South Africa.
Location
South Africa.
Methods
We used publicly available long-term datasets, the Southern African Bird Atlas Project and University of Delaware Gridded Climate Database, and spatial data from government bodies, to assess relationships between pied crow population and range changes, land use, infrastructure, urbanisation and climate change.
Results
Pied crow numbers have increased significantly in the past three decades, but rate of increase varied geographically, with crows declining in the northeast and increasing in the south-west of South Africa. Pied crow population changes were strongly correlated with climate change. Crows have benefited most from climate warming in the shrubland biomes of south-western South Africa. Pied crows are tree nesters, and within these shrublands, there is a strong positive relationship between the rate of population increase and the density of powerline infrastructure, which may facilitate pied crows’ increase by providing nesting sites.
Main conclusions
Pied crow numbers have increased in response to climate warming, with their spread facilitated by electrical infrastructure in south-western South Africa, providing a clear example of compound influence of multiple global change drivers promoting a significant change in species range and reporting rate. Pied crows are generalist predators and there is popular concern about their ecological impact in areas where increases have occurred. We highlight the importance of understanding the ecosystem-level implications of increased numbers of pied crows in South Africa's shrubland biomes.

Link: http://onlinelibrary.wiley.com/doi/10.1111/ddi.12381/abstract