DryFowlers
Babbler area in drought (picture Louis O’Neill)

Babbler and zebra finch fieldwork is underway at Fowlers Gap again in what is shaping up to be the worst drought since our work began out there in 2004. The long-term average amount of annual rainfall at Fowlers is 235mm. Since September 2016, there has been a total of 181mm across 23 months. In 2017 there was a total of just 77mm which makes it the second driest year from the 60 years for which data is available (Data from Bureau of Meteorology). So far, 2018 is looking even worse, with less than 3mm of rain recorded in the first seven months of the year.

As illustrated above, the environment is already looking extremely dry and the heat is just starting to pick up in the late winter, which will further dry the environment and challenge the animals and plants at the research station. Not surprisingly, in the work to date, there is no evidence that any of the birds are starting to breed, and the whole landscape is in urgent need of a drink.

Effects of El Niño Southern Oscillation on avian breeding phenology

Our recent work investigating the effects of the southern hemisphere climatic oscillations La Niña and El Niño on the timing of breeding by 64 temperate breeding species, and 15 species breeding in the arid zone. As illustrated below, La Niña is characterisedEnglertDuursma Fig1 by milder wet conditions in the main avian breeding period, and in such years, egg laying periods were typically longer for most species. There was a lot of variation in the response of different species and partly this was related to whether they breed early in spring. We found no obvious adverse effect of dry La Niña conditions, contrary to a prior expectation.

This study represents the most intensive examination of the effect of the southern climatic oscillation on breeding phenology in Australian birds and is focused on over 80,000 breeding records collected by a wide variety of sources over the past century.

The full paper can be found here.

The genetic structuring of the introduced house sparrow population across Australia and New Zealand

Sam’s paper characterising the structure of the house sparrow populations across Australia and New Zealand, was recently published in Biological Invasions.

SparrowStructure
The structure plot, illustrating the clusters of populations, based on their genetic structure From Fig 2. Andrew et al (2018)

The main conclusion of this work is that the population genetic structure of the house sparrows across Australia and New Zealand today, largely reflects the historical introductions of these populations, that were founded by deliberate introductions in the 1850-60s, by the Acclimatization Societies that were active in New Zealand, and multiple cities across Australia. As well as confirming the historical records concerning the site of independent introductions, the strong structure that we have characterised suggests limited movement between many populations. This is interesting because it provides the opportunity for selection to act on contemporary populations fairly independently and local adaptation may result, particularly given the range of climates and ecological variation faced by the different populations.

Andrew SC, Awasthy M, Bolton PE, Rollins LA, Nakagawa S, Griffith SC, (2018) The genetic structure of the introduced house sparrow populations in Australia and New Zealand is consistent with historical descriptions of multiple introductions to each country. Biological Invasions, 6, 1507-1522.

Epigenetics and the introduced populations of the house sparrow in Australia

Sparrowfig
The relationship between genetic differentiation between populations and epigenetic variation (Fig from Sheldon et al 2018)

In our most recent paper, published today in Royal Society Open Science (see article here), we examine the extent to which DNA methylation is related to genetic variation across different populations in the three introduction clusters of the house sparrow in Australia. We found no support for the idea that epigenetic variation might compensate for a lack of genetic diversity in introduced populations. However, we did find that patterns of epigenetic variation are highly variable across populations within each of these clusters, rather than having shared similarity across clusters (as in genetic variation). This study is still one of relatively few that has examined  the patterns of epigenetic variation across a number of populations and contributes to our growing understanding of the role of epigenetic variation in ecology and evolution.

It is particularly timely that the study is published today, the last day at Macquarie for both Ellie Sheldon who is departing to work on a field project in the Kimberley region, and Sam Andrew, who is heading to Finland to work with Craig Primmer on his Endeavour Fellowship.

Egg-shape and climate

Daisy’s second published paper from her PhD research is published today in Scientific Reports and is Open Access and can be downloaded here.

The media release for this story is below and explains the main findings and their implications.

EggShape
All of these species lay their eggs in open-cupped nests. The three species at the top breed in moist habitats, whereas the three at the bottom breed in the dry and hot desert regions, and their eggs are noticeably rounder.

New scientific study examines why eggs are shaped as they are

  • The shape of a species’ egg is determined by the climate in which they typically breed, and the extent to which their nest protects the egg from the sun.
  • The classically-shaped eggs with which we are so familiar have a greater surface area to volume ratio than a spherical egg, allowing for a greater level of gas exchange between the embryo and the environment.
  • As Easter approaches and the shops are full of chocolate eggs, it is a good time to be wondering why bird eggs are egg shaped and not nice round balls.

A new study published today in Scientific Reports by scientists from Macquarie University helps us understand why the classic egg shape evolved in birds and explains some of the species variation in egg shape.

The study examined egg shape in over 300 species of Australian birds, that live across some of the most extreme climates on earth, from the wet and humid tropics, to the dry and hot inland deserts.

The study found that the shape of a species’ egg is determined by the climate in which they typically breed, and the extent to which their nest protects the egg from the sun.

The most spherical eggs were typically found in desert species nesting in open nests, where the embryo inside the egg is likely to be damaged by the heat from the sun and dehydration. The most elongated or ‘egg-shaped’ eggs were found in moist environments, or in species that have enclosed nests, which are not exposed to the elements.

Lead author Daisy Duursma from the Department of Biological Sciences said as Easter approaches and the shops are full of chocolate eggs, it is a good time to be wondering why bird eggs are egg shaped and not nice round balls.

“There is a tension between allowing oxygen to get inside the egg so the embryo can breathe, but at the same time not allow too much moisture to escape and risk dehydration”.

The classically-shaped eggs with which we are so familiar have a greater surface area to volume ratio than a spherical egg, allowing for a greater level of gas exchange between the embryo and the environment.

The classic egg-shaped eggs are laid in relatively protected environments and prioritise gas exchange for the developing embryo to breathe, in a context where dehydration is less of a concern. The opposite is true in harsh environments where eggs are exposed to the elements.

“The egg shape is an adaptation that balances the need for the embryo to breathe without losing too much water, and can be nicely seen by looking at the eggs that are laid by different species across the diverse continent of Australia,” concluded Professor Simon Griffith, the leader of the project.

Readiness to breed is related to condition and stress across populations of zebra finch in the Northern Territory

OndiMap
The location of the five populations studied across the Northern Territory

Well done to Ondi Crino (now at Deakin University), who today saw her paper published, focused on probably the most remote field sites that we’ve worked on to date. Ondi measured the condition of birds across these five different sites, which all faced different ecological conditions, likely due to the different rainfall that they had experienced over the couple of years prior to the sampling. Birds in the different locations were in different condition and their stress hormones reflected this. Both things were correlated with the amount of breeding activity that we found across these five populations. The study is a step towards understanding the mechanisms underlying the opportunistic breeding that is seen in so many Australian birds – where birds will only breed when the local conditions are good. The paper was published today in General and Comparative Endocrinology and can be found here.

Phew – the effect of heat waves on sperm

Zebs hot

Lori’s work on the effect of heat on sperm quality was recently published in Proceedings of the Royal Society, Series B, and attracted some nice coverage in the media.

Lori also put together a nice blog with more pictures and videos for the Nature Ecol and Evol web site. That can be seen here. The original paper can be found here.

Body size is related to climate in sparrows and finches

We have published two recent papers (led by Sam Andrew), that show how body size of adult birds appears to be shaped by the climate during development. The first of these, published in Auk (link), is an observational study of the house sparrow across Australia, showing that in hotter areas sparrows are smaller. This pattern, consistent with findings in North America and Europe, is better explained by hot summer temperatures, than cold winter temperatures, and we believe suggests that development might be constrained by growing in hot conditions.

This idea was then supported by experimental work (along with some field observations) from the zebra finch. In this study (published in Journal of Evolutionary Biology) (link) we showed that birds that were reared in temperature controlled rooms at 30ºC were smaller than their full siblings reared at 18ºC. This is one of the first experiments to show that the ambient temperature effects development and body size in a warm-blooded animal.

Hatchling finch

MRes and research opportunities at Fowlers Gap

Fowlers montage

We are running a special field trip to Fowlers Gap from Monday 4th December to Tuesday 12th December for students who are keen to explore research opportunities with our research group. Fowlers Gap is an Arid Zone Research Station just to the north of Broken Hill (for more info on the station check out the link above).

We will take the best 6 applicants out there and cover transport, accommodation and food costs. Applicants will be expected to help out on two active research programs – one on sheep and the other on zebra finches. Applicants will be selected on the basis of their grades and the 400 word summary of why they would like to take part in either one of these research projects. More details on these projects can be found on this website.

This is a great opportunity for those interested to get to visit the iconic Australian outback and see species such as red kangaroos, emus, zebra finches and budgies in this spectacular environment.

As well as helping us with research you will get a chance to interact with members of the research group and explore opportunities for your own research projects at Fowlers Gap in the future. We are actively trying to recruit students into second year MRes and PhDs.

To express interest please contact either Stephan Leu or Simon Griffith by email.

To apply to come on this trip please submit an application as a single PDF providing the 400 word summary above as well as the grades that you achieved in any 300 level courses you have taken to date.

Closing Date for applications 15th October

Peri submits the final version of her thesis on the conservation genetics of the Gouldian finch

PeriThesis

Well done to Peri, who today submitted the final copy of her thesis to the library. Peri’s PhD thesis was well received by the three examiners who all recommended ‘award without corrections’. This was a great achievement, and we are very proud of her. Peri will be setting off to East Carolina University in July for an Endeavour scholarship.