Gardner, Janet L., Rowley, Eleanor, de Rebeira, Perry, de Rebeira, Alma, and Brouwer, Lyanne (2018) Associations between changing climate and body condition over decades in two southern hemisphere passerine birds. Climate Change Responses, 5. 2.

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Abstract

Background: Climate change presents considerable challenges for endotherms because they must maintain high, relatively constant body temperatures across a range of environmental conditions to ensure survival and optimise performance. Individuals exposed to changing weather must manage energy and water allocation to maintain thermal homeostasis, with consequences for body condition, and hence there is potential for selection because body condition is strongly linked to fitness. Understanding how weather drives changes in body condition is therefore fundamental to understanding how fitness is affected by climate change. Here we test for associations between weather and body condition and how this changes over time, in two co-existing species of small insectivorous passerines, the red-winged fairy-wren, Malurus elegans and white-browed scrubwren, Sericornis frontalis, that have been the subject of a ringing study for 39 years in temperate south-western Australia. The study populations have experienced increases in minimum temperatures in winter and summer as well as decreases in the frequencies of days with thermal minima < 5 °C, but the summer climate remains relatively mild with few days experiencing thermal maxima > 35 °C. Although, warming temperatures may reduce thermoregulatory costs, repeated exposure to hot conditions has been shown to have negative effects on body condition. Thus, we predict that the reduction over time in daily minima < 5 °C, along with the influence of increased maximum and minimum temperatures in summer and winter, will have positive effects on body condition.

Results: In accordance with thermoregulatory predictions, colder daily minima in the range 1–19 °C prior to capture were associated with reduced body condition in winter in both species. Furthermore, in summer, in fairy-wrens but not scrubwrens, warmer daily maxima were associated with increasing body condition, and repeated exposure to temperatures > 30 °C over consecutive days was negatively associated with body condition. Body condition increased over the 39 years of the study for fairy-wrens but there was no change in scrubwrens, which is consistent with observed within-season associations between body condition and weather, and the change in climate over time.

Conclusions: We show that associations between body condition and weather variables are complex and dynamic, with seasonal trends in body condition resulting from a balance between multiple, competing weather variables. Moreover, temporal trends in body condition over years could be predicted from the relative strength of seasonal trends and the direction and magnitude of changing climate. Because body condition is predicted to be strongly tied to both reproduction and survival, changes in climate may be having complex and far reaching consequences for demography mediated through shifts in body condition. Finally, subtle differences in the sensitivities of the species to weather variables led to different trends in condition over time which may be associated with differences in the capacity for behavioural thermoregulation. Understanding the causes of such sensitivities is vital in improving capacity to predict species responses to climate change.

Item ID:	71468
Item Type:	Article (Research - C1)
ISSN:	2053-7565
Keywords:	Behavioural thermoregulation, Body condition, Climate change, Meliphagoidea, Passerine birds, Australia
Copyright Information:	© The Author(s). 2018 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
Funders:	Australian Research Council (ARC)
Projects and Grants:	ARC DE130100174, ARC FT150100139
Date Deposited:	01 Feb 2022 06:11
FoR Codes:	41 ENVIRONMENTAL SCIENCES > 4101 Climate change impacts and adaptation > 410102 Ecological impacts of climate change and ecological adaptation @ 60% 31 BIOLOGICAL SCIENCES > 3103 Ecology > 310307 Population ecology @ 20% 31 BIOLOGICAL SCIENCES > 3104 Evolutionary biology > 310408 Life histories @ 20%
SEO Codes:	28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280102 Expanding knowledge in the biological sciences @ 100%
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