Data useMasters Project
RationaleDegradation and fragmentation of forest ecosystems by logging and conversion to agricultural systems is an ongoing and significant global issue. The development of oil palm as a high-yield crop has resulted in an unprecedented rate of conversion of Southeast Asian rainforests over the last half-century, leaving most remaining forest in effectively isolated fragments. Many studies have identified sharp declines in abundance and species richness in tropical bird species within communities as a result of this regime of degradation, fragmentation and conversion. However, few researchers have quantified the mechanisms that drive these trends, and whether or in what way degraded and fragmented environments can support the remaining avian communities. I intend to study the physiological and behavioural responses of tropical understory birds to recent degradation and fragmentation in a Southeast Asian forest, investigating feeding regime adaptation and stress in species that persist in degraded habitats as well as in their original, primary forest habitat. Food productivity and availability have been shown to correlate to bird species richness and abundance, and those bird species which suffer least in logged forests tend to belong to generalist feeding guilds. Therefore, diet is likely to strongly impact on the nutritional stress experienced by a species, and thus its fitness in an environment. I hypothesize that physiological measures of avian stress will increase across a gradient of fragmentation, and that dietary generalists will show reduced stress in comparison to dietary specialists in degraded habitats and forest fragments. I also predict that species that incorporate novel food items into their diet will exhibit less stress than species that do not. I will test this through ptilochronology, measurement of fluctuating asymmetry and faecal diet analysis, using the growth stress exhibited by feathers and fluctuating asymmetry in morphometrics as proxies for overall stress.
MethodsThis study will be carried out at the Stability of Altered Forest Ecosystems project, and the Maliau Basin Conservation Area in Sabah, Borneo, Malaysia. Sampling will be carried out in 10-hectare fragments within blocks A, B, C, D, E, and F, logged forest, oil palm plantations, and old-growth forest at Maliau. 100 meter transects will be established at 0m, 100m, and 250m from the forest edge and in the core of the fragment; transects will be re-sampled three times between February and July 2018. Mist nets with a 36mm mesh will be set up at each site for one day, and the sites will be netted in rotation. Birds captured in mist-nets will be removed and placed in individual cloth bags. The cloth bags will be lined with brown paper with a white card insert at the base to capture faecal deposits, which will be collected from the card insert and placed in plastic tubes, along with 70% ethanol solution, shown to sufficiently preserve DNA in avian faeces (Oehm et al. 2011). Morphometric measurements will be taken for both tarsi and both wings to capture fluctuating asymmetry as a measure of developmental stress (Lens et al. 1999). Two rectrice feathers will be collected to allow precise ptilochronological measurement. Faeces will be examined under stereo microscope in the lab to identify particulate remains of food items, such as insect exoskeletons; a CTAB DNA extraction kit will then be used on homogenized samples, and the DNA exported to the University of Florida for sequencing. Rectrice growth bars will also be measured in the lab. The average of the ten growth bars between the second and distal third of the feather vane of the collected rectrices will be used to estimate average feather growth as a proxy for nutritional stress (Carbonell & Tellerfa 1999), and standardised according to tarsus length to exclude body size effects.