The impact of high temperatures on foraging behaviour and body condition in the Western Australian Magpie Cracticus tibicen dorsalis §

Abstract

High temperatures can pose significant thermoregulation challenges for endotherms, and determining how individual species respond to high temperatures will be  important for predicting the impact of global warming on wild populations. Animals can adjust their behaviour or physiology to cope with higher temperatures, but the physical costs of these changes are not well known. We assessed the effect of  temperature on foraging behaviour, thermoregulatory behaviour and body condition in a wild, habituated population of Western Australian Magpies Cracticus tibicen dorsalis. Focal observation techniques were used to record individual behaviours, and body mass change was measured across a wide range of air temperatures. We found that temperature had a  significant effect on behaviour, with temperatures exceeding 27 °C resulting in a significant decline in foraging effort. Individuals
increased heat dissipation behaviours as temperatures rose, leading to a trade-off between foraging and heat dissipation.   Individuals lost body condition over the five-month summer period, but there was no significant difference in the daily change in body mass on cool days versus hot days. Our research reveals significant changes in daily behaviour in accordance with   temperature, but did not detect a measurable cost of this change. We therefore conclude that rising temperatures are likely to impact the behaviour of individuals in wild populations, but the potential flow-on effects of these behavioural changes are unclear.

Keywords: Australian Magpie, body condition, body mass, Cracticus tibicen  dorsalis, foraging effort, heat dissipation, high temperature, temperature dependent behaviour, trade-offs