Seabird Ontogeny in an Antarctic Environment. Threats, Coping Strategy and its Consequences for Wilson's Storm-petrel Chicks
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https://doi.org/10.22029/jlupub-20860Zusammenfassung
In the extreme environments of polar areas, time for offspring rearing is limited by environmental conditions for many animals. The completion of all body structures and functions in time as well as juvenile survival is linked to efficient development. Additionally, poor weather or foraging conditions may force long-live species with high adult survival rates like procellariiform seabirds to abandon their egg or chick to ensure their own survival in case of elongated breeding periods. Yet, seabird chicks are not only dependent on their parents' care and environmental conditions. During the last decades several anthropogenic threats were detected that may impair chick development and survival.In my thesis I studied anthropogenic, environmental and biological influences on the ontogeny of a procellariiform seabird, the Wilson's Storm-petrel (*Oceanites oceanicus*). Chicks of this species are known to be spontaneously reversibly able to reduce their body temperature and metabolism (facultative hypothermia). This is considered as a survival strategy to preserve energy. I identified body condition for unfed chicks as crucial factor to determine if they could maintain a constant body temperature between 36 °C and 41 °C or not (Chapter 1). After periods of unpredictable feeding that followed snowstorms, facultative hypothermia occurred almost in all chicks for several days until they could recover. Next, I examined the potential consequences of facultative hypothermia use to preserve energy resources, on developmental processes (Chapter 2). Low body temperatures had negative influences on growth, immune parameters, and fat physiology. Growth rates, that were reduced by hypothermia, recovered soon after rewarming. To evaluate if a chick could recover from e ects of facultative hypothermia on other physiological parameters or if its development with regard to these might be slowed down, the available data was insufficient. Lastly, I evaluated anthropogenic pollutants that accumulated in embryos through transfer of nutrients from yolk and albumen, which the mother collects during a prey-laying exodus and deposits to the egg (Chapter 3). Embryos were contaminated with legacy pollutants like polychlorinated biphenyls (PCBs), metabolites of dichlorodiphenyltrichloroethane (DDT), and mercury (Hg), and their PCB concentrations were higher than species with similar diets. Among samples collected during different years, those had higher PCB and Hg concentrations that were about ten years older. Concentrations of DDT metabolites remained similar among the differently aged samples.
Concluding, in the current environmental conditions, Wilson's Storm-petrel chicks can cope with weather extremes and unpredictable feeding by using facultative hypothermia, and seem able to recover from physiological setbacks regarding growth during hypothermia. In addition, they face high concentrations of pollutants from the very beginning. As seabird populations are declining worldwide, awareness of threats at all life-history stages is crucial to act successfully on their protection.