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Title
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Physiological stress as a mechanism underlying the effects of forest logging on tropical birds
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Author
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Abstract
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| Land-use changes are one main cause of biodiversity loss. Selective logging is the most common technique of timber extraction applied to tropical forests, driving species loss and population abundance changes. One main question to understand species’ responses to selective logging is which proximate mechanisms underlie species abundance changes. In this Ph.D. project I have used a cross-sectional approach to investigate the effects of selective logging on the stress physiology of understorey birds, and correlative analyses to investigate the effects of physiological changes on population abundance, across unlogged and selectively logged forest of Borneo. The first goal of the project was to determine which physiological endpoints of vertebrates are affected by forest disturbance. To this end, I reviewed all available literature and used meta-analytical techniques to quantify the size of the effects of different forest disturbances, including selective logging, on physiological and immunological parameters. I have then investigated the effect of selective logging on the activity of the hypothalamic-pituitary-adrenal (HPA) axis in 10 understorey bird species. I used as marker of HPA axis activity the concentrations of corticosterone, the avian glucocorticoid hormone, deposited in feathers. Another important physiological mechanism for maintaining homeostasis is the regulation of cellular oxidative status. Thus, I measured eight different markers of oxidative status in 15 understorey bird species living either in unlogged and selectively logged forests. I also investigated differences in the oxidative status between feeding guilds (i.e. insectivores and omnivores) and how they are affected by selective logging. Last, I tested for differences in body size and body condition of more than 50 bird species across unlogged and selectively logged forests. Changes in body size and body condition can be sub-lethal effects of habitat degradation that may act as early signals to predict future population responses. This hypothesis was tested correlating changes in body size and body condition with changes in population abundance between the two types of forest. Results point to feather corticosterone as a promising tool for monitoring the impacts of sylvicultural practises on understorey birds. There is little long-term effect of logging on the oxidative status of understorey bird species. Last, frugivores and omnivores have reduced body size in the logged forest compared to unlogged, pointing to potential functional consequences related to seed dispersal. |
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Language
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English
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Publication
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Antwerp
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University of Antwerp, Faculty of Science, Department of Biology
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2021
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Volume/pages
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167 p.
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Note
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Costantini, David [Supervisor]
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Edwards, David P. [Supervisor]
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Eens, Marcel [Supervisor]
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Full text (open access)
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