Jenni-Eiermann, S., B. Almasi, C. Müller, B. Schmid, A. Roulin & L. Jenni
(* = Kurzbeitrag)
Die Modulation der Stressantwort bei Vögeln und ihre Bedeutung für den Naturschutz.
(von 1994 bis 2006 vergeben)
Stress, Corticosteron, Stressachse, Stress-Sensibilität, Energiereserven, Lebenserwartung, Fortpflanzungsaussichten, genetische Variation, Naturschutzbiologie
Tetrao urogallus, Tetrao tetrix, Parus caeruleus, Parus major, Tyto alba, Sturnus vulgaris, Falco tinnunculus, Upupa epops
Auerhuhn, Birkhuhn, Blaumeise, Kohlmeise, Schleiereule, Star, Turmfalke, Wiedehopf
Modulation of the stress response in birds and its meaning in nature conservation. During threatening situations birds react with the activation of the hypothalamo-pituitary-adrenal axis (HPA-axis). Corticosterone, the main glucocorticoid in birds, is released from the adrenal cortex into the circulation in high concentrations and delivered to the organs. There corticosterone triggers metabolic and behavioural changes which help to overcome the dangerous situation and to restore homeostasis. This activation implies costs: reproductive activities and immunity are suppressed and energy stores are mobilized. Therefore a bird has to balance its stress response in a way that the benefits outweigh the costs. We present 3 studies investigating the questions (1) which factors can affect the activation of the HPA-axis and (2) whether the variation of the stress response shows a long-term effect. The first study investigated the interaction between fat reserves and stress response of nestlings of the Common Kestrel Falco tinnunculus. Nestlings without fat reserves had an elevated baseline corticosterone level and a dampened stress response indicating a stressful state. The second study investigated whether the stress response of Eurasian Hoopoes Upupa epops depended on the brood value. Hoopoe parents during the first of two annual broods or with an early single brood showed a higher stress response than parents with the second brood or breeding late in the season. The results confirmed the brood-value-hypothesis postulating that parents with the chance for a second brood invest more in their own survival than parents with only a small chance for a future brood, which invest more into the current brood. The third study showed that the activation of the HPA-axis is genetically regulated. Small-spotted Barn Owls Tyto alba reacted with a higher stress response than large spotted Barn Owls. Depending on the environmental conditions the different stress response was advantageous for one of the two colour variants. Finally the role of corticosterone measurement as a tool in conservation biology is discussed. It offers a measure to identify stressors which would otherwise not have been detected. It also offers a measure to identify the ability of an individual to cope with stress and whether in the long-term a stressor might have a selective effect.
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