Past and future potential range changes in one of the last large vertebrates of the Australian continent, the emu Dromaius novaehollandiae

In Australia, significant shifts in species distribution have occurred with the loss of megafauna, changes in indigenous Australian fire regime and land-use changes with European settlement. The emu, one of the last megafaunal species in Australia, has likely undergone substantial distribution changes, particularly near the east coast of Australia where urbanisation is extensive and some populations have declined. We modelled emu distribution across the continental mainland and across the Great Dividing Range region (GDR) of eastern Australia, under historical, present and future climates. We predicted shifts in emu distribution using ensemble modelling, hindcasting and forecasting distribution from current emu occurrence data. Emus have expanded their range northward into central Australia over the 6000 years modelled here. Areas west of the GDR have become more suitable since the mid-Holocene, which was unsuitable then due to high precipitation seasonality. However, the east coast of Australia has become climatically sub-optimal and will remain so for at least 50 years. The north east of NSW encompasses the range of the only listed endangered population, which now occurs at the margins of optimal climatic conditions for emus. Being at the fringe of suitable climatic conditions may put this population at higher risk of further decline from non-climatic anthropogenic disturbances e.g. depredation by introduced foxes and pigs. The limited scientific knowledge about wild emu ecology and biology currently available limits our ability to quantify these risks

Male parental care in the polyandrous emu, Dromaius novaehollandiae

The ratites, including the Australian emu Dromaius novaehollandiae, are one of the few groups that engage in polyandrous and promiscuous mating, but the male alone cares for clutches with mixed maternity and paternity. Male only parental care is uncommon (2% of avian species) and the coupling of male only parental care with polyandry, presents an interesting phenomenon in the study of mating systems. Despite this, limited research has been conducted on male only parental care with polyandry, and behavioural and reproductive success has been relatively unstudied in the emu. This project aims to investigate male parental care and reproductive success in the emu. I look predominately at male investment in incubation and its correlations between clutch traits, egg traits and parentage, using a free-ranging captive population to perform observational and manipulative studies. I also investigate changes in climate suitability of emus across Australia, indicating how this may be driven by winter breeding. This work aims to address the following questions: 1) A review of the evolutionary divergence of mating systems in the ratites; 2) Are egg and clutch traits under selection that is mediated by hatching success for increase parental and offspring fitness? 3) What is the optimal clutch size in the emu and is hatching success limited by the male incubation capacity? 4) Does paternity drive male investment in incubation? 5) What determines emu distribution across Australia and is distribution likely to change under past and future climate scenarios? The findings of this thesis provide insights into the uncommon coupling of polyandry with male parental care, indicating the potential benefits of polyandrous and promiscuous mating not only for the female but also for the male emu. My findings may not only help to inform future studies on the evolution and maintenance of parental care and mating systems, but also future management strategies of this species

S1Ldata

Data of time spent on one leg across temperatures, with tarsus and body weight

Data from: Leg length and temperature determine the use of unipedal roosting in birds

The function of standing on one leg in birds has long been attributed to reducing heat loss from the unfeathered legs to the external environment. Whilst a handful of single-species studies correlate the use of the behaviour with ambient temperature, the degree to which it is used across taxa is unknown. Given that leg-length varies between species, the length of the leg (relative to body size) may mediate the use of this thermoregulatory behaviour, such that birds with longer legs should roost on one leg more than those with relatively shorter legs at any given ambient temperature. We tested this prediction through field observations and comparative analyses of nine shorebird species, with varying tarsi length relative to body size. Six of the nine species examined used unipedal standing more as temperatures decrease, indicating it’s role as a heat conservation behaviour. We also found that species with relatively longer legs roosted on one leg more frequently across a wide range of temperatures. Species with shorter leg lengths likely rely less on this posture to insulate the relatively smaller surface area of the legs. Our findings showed that the long accepted notion that birds stand on one leg more at colder temperatures, holds, and that species with smaller relative leg length were less reliant on this behaviour to minimise heat loss from these bare appendages

Measurement techniques for curved shorebird bills: a comparison of low-tech and high-tech methods

The morphology of the bill is an important aspect of many avian ecological and biological studies. Most studies report the straight line length of the bill; however, for birds with curved bills, this may underestimate the overall length. Here we describe and compare low-tech physical and high-tech digital methods of measuring the curved length of the bill, using measurements from two shorebird species, Red-necked Avocet and Curlew Sandpiper. For the low-tech estimates we used (1) callipers and (2) string placed along the curve of the bill. For the high-tech estimates we used digital measurements of high quality photographs. Additionally, these methods are used to measure several other bill metrics, including bill height and middle bill profile. Whilst both methods can be used with relative ease, the combined use of both methods in intra- and inter-specific comparison should be avoided since they produce significantly different estimates. These differences suggest that further research should be undertaken to determine which method is more accurate. Our findings have implications for the current, standard physical method for measuring curved bills

Leg length and temperature determine the use of unipedal roosting in birds

The function of standing on one leg in birds has long been attributed to reducing heat loss from the unfeathered legs to the external environment. Whilst a handful of single-species studies correlate the use of the behaviour with ambient temperature, the degree to which it is used across taxa is unknown. Given that leg-length varies between species, the length of the leg (relative to body size) may mediate the use of this thermoregulatory behaviour, such that birds with longer legs should roost on one leg more than those with relatively shorter legs at any given ambient temperature. We tested this prediction through field observations and comparative analyses of nine shorebird species, with varying tarsi length relative to body size. Six of the nine species examined used unipedal standing more as temperatures decrease, indicating its role as a heat conservation behaviour. We also found that species with relatively longer legs roosted on one leg more frequently across a wide range of temperatures. Species with shorter leg lengths likely rely less on this posture to insulate the relatively smaller surface area of the legs. Our findings showed that the long accepted notion that birds stand on one leg more at colder temperatures holds, and that species with smaller relative leg length were less reliant on this behaviour to minimise heat loss from these bare appendages

The importance of wetland margin microhabitat mosaics; the case of shorebirds and thermoregulation

Wetlands, and the species that rely upon them, are under significant threat world-wide, with wetlands often being completely removed or drastically altered. Successful wetland management requires an understanding of the interactions between wetland species and the microhabitats they use. The use of microhabitats for thermoregulation in wetland species is poorly studied, though anthropogenic influence on wetlands can reduce the diversity of microhabitats and thus the thermoregulatory options for animals. At high ambient temperatures birds may use the water-logged wetland margins to help with thermoregulation, and are often observed roosting in the sitting position within this microhabitat. However, whether sitting on the wet substrate helps in thermoregulation is unknown. In this study, we tested whether birds selectively use microhabitats across temperatures by conducting field observations of nine species of shorebirds. We use comparative analysis to determine whether birds roost more on wet substrate in the sitting posture, that is, ‘wet-sitting’, at high ambient temperatures. We found substrate type across the wetland margins to be important in shorebird thermoregulation, with the time spent sitting being significantly mediated by the substrate on which the bird roosted. Individuals tended to sit on bare, wet ground much more under high ambient temperatures compared with low ambient temperatures. Vegetation on the other hand was used similarly across temperatures, and likely does not provide the same thermoregulatory benefits. By roosting on wet substrate at high ambient temperatures, birds may increase the potential for heat dissipation across the uninsulated legs, as water-logged wetland margins are known to remain cooler than the ambient temperature or vegetated microhabitats under hot climatic conditions. Synthesis and applications. Wetland creation and management requires an understanding of the functional significance of such microhabitats, not only for foraging and breeding, but also for roosting. We demonstrate that managing wetland margins is likely important in minimising heat stress in birds, with our findings emphasising the importance of maintaining open spaces in habitat mosaics for birds to use for thermoregulation. The ability of wetland species to manage heat stress is becoming exceedingly important as they are threatened by both decreased wetland availability and increasing ambient temperatures under climate change

A novel observation of food dunking in the Australian Magpie Gymnorhina tibicen

We document putative food-dunking behaviour in the Australian Magpie Gymnorhina tibicen. While conducting an experiment on the Mountain Katydid Acripeza reticulata, we presented one to a wild adult Magpie, which appeared to conduct 'dunking behaviour' while processing the insect. The Magpie carried the katydid to a puddle of water, dunked the katydid, and then dropped it. A nearby juvenile Magpie then retrieved the katydid and performed the same dunking behaviour before eating the katydid. To our knowledge, this is the frst reported instance of food dunking by Australian Magpies. We hope this observation will facilitate future investigations into behavioural adaptations to dietary choices of Magpies