Zebra finches help to shine a light on the social function of bird song

In a paper published today in Current Biology, we have characterised the very social nature of song in the zebra finch, and this helps to highlight the fact that bird song is not always about competition over mates and territories. In the study, led by Hugo Loning, a student in Marc Naguib’s research group in Wageningen University (Netherlands), we have analysed the expression of song over several years and in a variety of contexts. The study is an amalgamation of data collected by remote acoustic recorders every three days at Fowlers Gap for several years, across a lengthy drought, and periods of breeding and no breeding activity. The main finding are that zebra finches sing a lot regardless of the season, or condition of the local environment. Males usually sing in the presence of their female partner (who they are typically paired with for life), and also in close company with other males. We believe that our findings should place a greater emphasis on the social function of birdsong more generally, and that it is a useful signal for the coordination of activity across a population of birds. Our findings are in contrast with the great majority of studies of bird song that emphasise the competitive nature of bird song.

There is a piece written about the work in Macquarie’s Lighthouse magazine which includes some video of singing males.

Assessing the danger of climate change to birds

Tito’s first paper was published today in Conservation Physiology. The paper, which includes some of Tito’s data, is a response to a recent model that had evaluated the likely effects of climate change on some of Australia’s birds. In our response, we used data from our study of the zebra finch to argue that the assumptions that are commonly made about the effects of a warming climate on birds are often over simplistic and aren’t able to account adequately for the adaptive responses that birds are likely to make. For example, in the paper we show that one of the important responses that birds will make on extremely hot days is to drink significantly more water than normal. If birds can stay adequately hydrated they are able to use that water to reduce their body temperature significantly and guard against hyperthermia. We also argue that there is an urgent need to get better physiological data from the zebra finch and other species to improve the value of predictive models in the future. The climate is changing and more extremely hot days are likely. That does cause a significant challenge for birds and there will be a tipping point for survival at some temperature. That point is likely to be slightly higher than the one predicted by earlier models though given the remarkable adaptive responses that we have demonstrated in the zebra finch. The full paper can be found here.

When it gets hot zebra finches drink more, and make use of the many artificial water points across the arid landscape such as this stock watering trough. (photo: Simon Griffith)

Tiarne’s thesis submitted

 The physiological effects of high blood lead levels in the House sparrow 

Congratulations to Tiarne Harris who submitted her MRes thesis today. Well done on all the amazing work you have put in over the past 12 months. I’m really excited about the results that you have found in the Broken Hill sparrows and the future research directions that they have stimulated.

Tiarne (left) and Lori out at Lex’s in South Broken Hill collecting some of her data.

The evolution of colourful eggs

It is great to see Kiara’s paper now published in Evolution (it can be found here). The paper is focused on the evolution of colour in eggs and uses the Australian passerines to provide insight into the emergence of pigmented eggs in different branches of the family tree. The passerines, are the songbirds, and they make up about half of the world’s species of bird today. This group first evolved in Australia, and the continent is still home to the largest number of passerine families, and can provide insight into what was happening early in the radiation of the group.

In this study we characterised the egg colour variation across different families of Australian songbird, and were able to identify that the ancestral egg colour in the passerine group was most likely to be white, and that pigmented eggs emerged independently in a number of different branches of the family tree over time. Importantly, this seems to have happened after the ancestors of the different families evolved open nests. This makes sense, because the pigment likely evolved to help protect the now exposed eggs from predators and from solar radiation.

This paper builds nicely on the earlier comparative work that was started with Jordan Price, when he visited on sabbatical and Daisy Englert Duursma.

Fig 2. from L’Herpiniere et al 2021, showing how the evolution of colour in the eggs of different species, maps nicely on to the distribution of closed and open nests across the phylogeny of Australian passerines.

Singing it softly

Singing male Zebra Finch. (Photo Hugo Loning)

Zebra finch song is an extremely short-range signal. That is the conclusion from the recent paper by Hugo Loning in Behavioral Ecology. This is the first paper of our project on acoustic communication of the wild zebra finch in collaboration with Marc Naguib from Wageningen University. After quantifying the song amplitude of wild zebra finch recordings, we played them back at natural amplitude and re-recorded them in our field site Fowlers Gap. Afterwards, we analysed these transmitted vocalisations while integrating what is known about the hearing from lab zebra finches. This way, we found out that the detection distance of song is on average about nine meters – an extremely short distance for song. We supported this claim by observations in the field which confirm that group members are often very close, on average within one meter, when a group member is singing. Additionally, we find that even their ‘distance call’ does not reach very far, up to about fourteen meters. Our reported findings are in stark contrast with the classical idea of birdsong as a long-range communication signal. The paper can be freely accessed here.

Cover Page Model

It clearly helps to work on an amazingly beautiful species when it comes to getting a cover page photo for a study, and once again a journal has chosen to use a picture of the Gouldian finch to grace the cover. Here is the August cover of the Journal of Experimental Biology with a great photo supplied by Mark Chappell, one of the co-authors of our new paper. The paper, led by Bill Buttemer demonstrates that although the red and blackheads morphs have some quite different behavioural strategies there is no difference in their basal and maximal metabolic rates.

A male black-headed and male red-headed Gouldian finch.

Mitonuclear incompatibilities in the two subspecies of the Long-tailed finch

It is really great to see our first paper in this exciting space being published with the paper by Kelsie Lopez being published in Evolution. The paper can be found here. In this paper we report the molecular work that Kelsie did with Daniel Hooper at Cornell, finding a divergence in the mitochondrial sequence of two clades that arose around 0.5 million years ago. This is the kind of spilt that recent theoretical work has suggested might help to drive speciation, and the incompatibility of two closely related forms (lots of cool work by Geoff Hill, and Paul Sunnocks in this area). This spilt in mitochondrial haplotypes is coincident with the Z chromosome divergence that we found earlier, and centred around Kununnurra in the Eastern Kimberley. Hybrid zone females are significantly less likely than males to carry an admixed Z chromosome or have mismatched Z-mitochondrial genotypes, which is a strong indication that there is some cool selection happening here. So a female that has a western Z chromosome, will work better if she also has a western mitochondrial haplotype. Females with a mismatch, like a western Z chromosome and an eastern mitochondrial haplotype are probably less fit and tend to perish at an earlier stag of development. We are following this up with more work in the field and laboratory.

Figure 2. From Lopez et al 2021.

Sperm, eggs, and nestlings – 2 days, 3 papers!

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.

Figure of Sperm Sizer in action. From McDiarmid et al 2021.

Why are pair bonds so strong in Australia?

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).

How do Zebra finches cope with heat?

Drinking zebra finches (Picture: Simon Griffith)

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).

Extrapair paternity in birds

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.

Fig 3 from paper, showing the level of EPP across different species across the avian family tree