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Acute and chronic heat stress risk in Kalahari Desert birds under past, present and future climates
Dissertation (MSc (Zoology))--University of Pretoria, 2018.
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| Language: | English |
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University of Pretoria
2025
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| _version_ | 1867613482004774912 |
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| access_status_str | Open Access |
| author2 | McKechnie, Andrew E. |
| author_browse | McKechnie, Andrew E. |
| author_facet | McKechnie, Andrew E. |
| collection | Thesis |
| dc_rights_str_mv | © 2024 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. |
| description | Dissertation (MSc (Zoology))--University of Pretoria, 2018. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/107100 |
| institution | University of Pretoria (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:36:50.758Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | University of Pretoria |
| publisherStr | University of Pretoria |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/107100 Acute and chronic heat stress risk in Kalahari Desert birds under past, present and future climates McKechnie, Andrew E. Woodborne, Stephan shannonconradie@gmail.com Conradie,Shannon UCTD Sustainable Development Goals (SDGs) Climate change Heat stress Avian biology Thermal modeling Physiology Dissertation (MSc (Zoology))--University of Pretoria, 2018. Earth’s climate is warming at an unprecedented rate, with climate change affecting virtually every habitat on the planet. Organisms can potentially adjust their physiology, behaviour, morphology and/or geographic distribution in response to changes in climate, although their capacity for such adjustments may be constrained by biotic and/or abiotic factors. Organisms’ niches are part of a dynamic system that responds to changing climates and has resulted in species distributional shifts in the past, and will surely continue to do so in the future. Past climate data combined with species responses to climate change provide a tool for predicting extinction risk and reducing uncertainty for species responses to future climate change. Trajectories of species distributions and extinction risk in response to changing environmental conditions have not considered climate histories and the physiological responses that organisms might have expressed. I developed a dynamic tool interrogating spatial-temporal climate models, allowing identification of areas of acute and chronic heat stress risk in arid-zone birds. Birds are particularly vulnerable to increased air temperatures (Ta) due to their predominantly diurnal lifestyle, small size, and their high energy and water requirements. When exposed to short-term (typically hours) increases in Ta, birds experience acute heat stress where their only avenue of heat dissipation to maintain body temperature below environmental temperatures is evaporative heat loss. The rate of evaporative water loss in response to air temperatures reveals critical thresholds (Tthresh) of lethal dehydration risk. All passerines modelled here experience occasional risk of lethal dehydration under current conditions, with the threat increasing in frequency, severity and geographic area under a high risk climate change scenario (RCP 8.5) by the end of the century. This is most obvious for Burchell’s Starling which will experience approximately 6 – 10 d·y-1 of risk over a large proportion of their range. Similarly Scaly-feathered Finches and White-browed Sparrow-weavers will be exposed to an increase in the number of heat stress days within and around their ranges. When hot weather persists over periods of days to weeks, birds experience trade-offs between foraging and thermoregulation which have chronic, sublethal negative impacts on individual survival and fitness. Currently species in southern Africa are experiencing < 10 consecutive days where Ta > Tthresh, however these conditions are likely to increase by approximately 830% for Southern Pied Babblers and Common Fiscals (Tthresh2), and 283% for Common Fiscals (Tthresh1) in the southern Kalahari Desert region, under large proportion of the breeding season. Given the expected increases in frequency and extent of high temperatures and the inability to maintain body condition at these temperatures, successful breeding attempts are likely to decrease by the end of the century in desert birds. I suggest that these chronic, sublethal effects will be more important in terms of species persistence than the risk of acute mortality events under future climate change. Zoology and Entomology MSc (Zoology) Unrestricted Faculty of Natural and Agricultural Sciences SDG-13: Climate action SDG-15: Life on land 2025-12-08T06:50:34Z 2025-12-08T06:50:34Z 2019-04 2018-09 Dissertation * A2019 http://hdl.handle.net/2263/107100 en © 2024 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. application/pdf University of Pretoria |
| spellingShingle | UCTD Sustainable Development Goals (SDGs) Climate change Heat stress Avian biology Thermal modeling Physiology Acute and chronic heat stress risk in Kalahari Desert birds under past, present and future climates |
| title | Acute and chronic heat stress risk in Kalahari Desert birds under past, present and future climates |
| title_full | Acute and chronic heat stress risk in Kalahari Desert birds under past, present and future climates |
| title_fullStr | Acute and chronic heat stress risk in Kalahari Desert birds under past, present and future climates |
| title_full_unstemmed | Acute and chronic heat stress risk in Kalahari Desert birds under past, present and future climates |
| title_short | Acute and chronic heat stress risk in Kalahari Desert birds under past, present and future climates |
| title_sort | acute and chronic heat stress risk in kalahari desert birds under past present and future climates |
| topic | UCTD Sustainable Development Goals (SDGs) Climate change Heat stress Avian biology Thermal modeling Physiology |
| url | http://hdl.handle.net/2263/107100 |