The past few days have been particularly productive for the research group with three quite different papers all published online over the past 48 hours. First up was the paper published in Ibis reporting the catastrophic mortality of nearly all embryos, during a heatwave back in 2017. The paper was written by Luke McCowan and myself, and describes this heatwave and the very high level of mortality throughout the population at this time. We will publish more detail on this one very soon.
Second up is the first experimental paper focused on data from the Oroboros Oxygraph machine that we have used to assay mitochondrial function. This paper, published in Frontiers in Physiology, was led by Riccardo Ton, and is focused on the experiment he conducted while first visiting us as an Endeavour Scholar in 2019. The paper is published online and is publicly accessible here.
Finally, less than 12 hours after Riccardo’s paper is the SpermSizer paper written by Callum McDiarmid. This paper, published in Behavioural Ecology and Sociobiology describes a new tool for measuring sperm morphology. The program has been extremely useful in processing the many thousands of sperm that we have now measured in our studies of estrildid finches. The paper can be found here.
The first fieldwork I ever did in Australia was focused on the silvereye. On my first day in the field, having worked in Europe up to that point, I was so struck by this pair allopreening that I took this photo (on the left). Since that time, one of the questions that I have worked on, has been why pair bonds in Australian birds are so different, and much stronger then those exhibited by similar birds in Europe.
Recently I published a review of empirical work in this area in Frontiers in Ecology and Evolution. The paper is open access, and can be downloaded here. We are continuing to conduct research in this area, with one of our main projects being a collaboration with Marc Naguib from Wageningen, focused on the pair bond and acoustic communication between partners in the zebra finch (pair shown on the right above).
In two papers recently published with our collaborator, Dr Christine Cooper from Curtin University, we have looked at the physiological mechanisms through which zebra finches can cope with the extreme conditions that occur regularly at our field site, and specifically air temperatures in excess of 40 degrees Celsius. The papers, published in the Journal of Experimental Biology and Comparative Biochemistry and Physiology, Part A, help us to understand how birds adjust their physiology to cope with such challenging conditions. Zebra finches were better able to cope with heat waves when they were primed by similar conditions, and reduced their metabolic rate, thus lowering the amount of heat being generated internally. Individuals also showed great plasticity in their use of water and their body temperature, enduring short periods with elevated body temperature when required. It is not surprising that these desert adapted birds can cope so well with these hot and arid conditions, but understanding the mechanisms that they can use, and the flexibility that they have helps us to understand likely responses to climate change in desert birds, and the reasons that mortality events have been reported in these and other desert specialists. It is likely that those heat induced deaths have been caused by unpredictable bursts of high temperature, which the birds were not able to prepare for.
For the first time in 15 years the zebra finches at Fowlers Gap, have had a bumper breeding event that has run right through the Austral winter. This followed rains that came in March and April, and brought the drought, that had meant that there was no breeding in the Spring of 2017, 2018 and 2019. The rain filled most of the dams on the station and produced enough winter grass for the crops of nestlings to be filled to bursting. The breeding started in May and has continued right through to the normal start of the breeding season (August).
Our review of extrapair paternity in birds is published today in Molecular Ecology and can be accessed here. The paper, written by Lyanne Brouwer and myself, is an update on the last review that I published on the subject in 2002. There are now over 30 years of molecular data on the incidence of extrapair offspring in socially monogamous species and we present an overview of over 500 studies focused on over 300 species. Overall, in around three quarters of socially monogamous species, some evidence of infidelity has been found. In the species in which it occurs about one fifth of all offspring are fathered by an extrapair sire, and therefore not by the social male who is investing in their care. We also demonstrate that the incidence of extrapair paternity is more likely to occur in some avian families, being particularly prevalent in passerines, and rarer, or completely absent in families that are long-lived, such as owls, or seabirds.
Our new paper has just come out, from work done at Fowlers Gap a couple of years ago. In the study we looked at how nestlings are affected by both very hot days and very windy days as they are developing in the nest. These conditions are stressful for nestlings, and we found that both types of bad weather affected the level of corticosterone – the stress hormone. These findings are likely to be driven both directly and indirectly. When nestlings are very hot, they find it hard to lose heat and that will be stressful itself. Wind can be stressful because the noise will mask the ability to hear other sounds in the environment, such as communication with parents, and also the noise of approaching predators. In addition, the results may be the indirect effect of hunger, as parents will find it much more difficult themselves to find food to feed to their nestlings when it is hot and windy. The work was led by Ondi Crino, who is an endocrinologist, and expert on stress. The paper can be found here.
In the second paper to be published from Hanja’s thesis, we have demonstrated that zebra finches would rather nest next to a pair that are also just starting to breed, than a pair that is further along. Hanja and team demonstrated this by erecting new empty nest boxes near to occupied boxes, at either nest-building, incubating or chick rearing stages. Pairs were far more likely to lay eggs in the experimental boxes that were close to those that had also initially been at the nest building stage. We believe that these results are driven by the social benefits of breeding alongside other pairs at a similar stage of activity. The paper is published in the journal Animal Behaviour, and can be downloaded for free in the next month using this link.
A paper by student Victoria Austin, completed while she was an MRes student in the lab has just been published, focused on the almost incessant singing of the chirruping wedgebill – a song that will be familiar to anyone who has worked at Fowlers Gap, or elsewhere in the range of this arid zone bird. The paper, entitled ‘Song rate and duetting in the Chirruping Wedgebill (Psophodes.cristatus): frequency, form and functions’ has been published in Emu – Austral Ornithology. The paper can be found here.
Even though it was extremely dry at Fowlers Gap this spring, our zebra finch field season was a successful one. Luckily for us, zebra finches were still present in large numbers despite the drought. Interestingly, zebra finches were still found singing actively although hardly any breeding attempts were made.
In a new collaborative project with Marc Naguib and Hugo Loning of Wageningen University, the Netherlands, we will look into more detail at wild zebra finches’ communication, especially singing behaviour. From lab studies we know that their song functions in mate choice when reaching maturity, but why they sing for the rest of their adult life remains unclear.
To this end we have installed a large number of passive acoustic monitoring devices which enables us to monitor the acoustic environment during and outside of breeding seasons, in a variety of habitats for years to come. This will not only contribute to zebra finches studies, but also gives us valuable information on the presence of other birds, which will benefit additional studies on bird ecology, migration and conservation in these unpredictable, extreme environments.
Our paper on genetic changes in response to Lead pollution in the outback towns of Broken Hill (NSW) and Mount Isa (Queensland), has been published in the journal, Science of the Total Environment. The paper, “Signs of adaptation to trace metal contamination in a common urban bird” focuses on changes in the frequency of 35 SNP’s linked to a number of genes, some of which have been shown to relate to the transfer of heavy metals across cell membranes.
The study, led by Sam Andrew, and part of his PhD project was done in collaboration with the team in Trondheim led by Henrik Jensen, and also Mark Taylor at MQ.
The study was covered by a few stories in the media and one of those stories can be found here. The article itself can be accessed here.
In September we conducted fieldwork on either side of the NT and WA border to sample long-tailed finches in the area where the eastern and western forms of the Z chromosome meet in the wild (see recent paper by Hooper et al (2018). The fieldwork team comprised Daniel Hooper and Emma Grieg (both from Cornell University), Kyle Kostrzewa, and Callum McDiarmid and Simon Griffith (Macquarie). The trip was successful and we had two weeks of camping, driving (a lot) and finding water holes and sampling birds in the area from Keep Rive in the east, to Home Valley station in the West.