An estimate of the water budget for the endangered night parrot of Australia under recent and future climates

Abstract

Endangered species management must now incorporate the potential effects of climate change, but this is often in the context of limited data. The endangered night parrot was recently rediscovered in the Australian arid zone and a major effort is underway to ensure its survival. A key question is to what extent it is dependent on standing water under current and future climates, as this has major implications for understanding and managing its habitat requirements. However, very little is known about its ecology and physiology, and its conservation status precludes invasive ecophysiological studies. Here we show how the methods of biophysical ecology permit strong inferences about this problem with minimal data. We developed a biophysical model of both the parrot and its habitat at the site of its rediscovery. We used allometrically-adjusted observations of the known physiology of a closely related desert-adapted Australian parrot, the budgerigar, to infer unknown aspects of the night parrot’s physiological responses, together with plumage measurements from museum specimens. We tested the microclimate model against empirical data on microhabitat temperatures and compared the endotherm model predictions against an infra-red thermograph of the bird itself. We then used the model to predict the frequency with which the parrot would need to find standing water under current and future climates depending on the water content of its food. Our field data show that air temperature in night parrot roosts during high summer typically exceeds the inferred resting core temperature (38 °C) and can exceed 45 °C. Our calculations imply that night parrots can persist on dry seed during winter conditions without exceeding dangerous levels of dehydration, but would need access to water or succulent (55% water) food during summer. Air temperature at the site is projected to increase 3 °C by 2070, which would lead to likely lethal (22% of body mass) levels of daily dehydration in some years even on succulent food, and would dramatically increase its dependence on standing water. Our findings have significant implications for the conservation management of the night parrot and provide guidance for future research priorities.