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Behavioral and physiological responses to unpredictable changes in environmental conditions are, in part, mediated by glucocorticoids (corticosterone in birds). In polymorphic species, individuals of the same sex and age display different heritable melanin-based color morphs, associated with physiological and reproductive parameters and possibly alternative(More)
Exogenous administration of glucocorticoids is a widely used and efficient tool to investigate the effects of elevated concentrations of these hormones in field studies. Because the effects of corticosterone are dose and duration-dependent, the exact course of plasma corticosterone levels after exogenous administration needs to be known. We tested the(More)
Stress generated by humans on wildlife by continuous development of outdoor recreational activities is of increasing concern for biodiversity conservation. Human disturbance often adds to other negative impact factors affecting the dynamics of vulnerable populations. It is not known to which extent the rapidly spreading free-riding snow sports actually(More)
Long-distance migrants regularly pass ecological barriers, like the Sahara desert, where extensive fuel loads are necessary for a successful crossing. A central question is how inexperienced migrants know when to put on extensive fuel loads. Beside the endogenous rhythm, external cues have been suggested to be important. Geomagnetic information has been(More)
Migration is a key life cycle stage in nearly 2000 species of birds and is a greatly appreciated phenomenon in both cultural and academic arenas. Despite a long research tradition concerning many aspects of migration, investigations of hormonal contributions to migratory physiology and behavior are more limited and represent a comparatively young research(More)
Birds may react to the presence of humans with an immediate primary behavioural reaction and with physiological responses, such as the activation of the hypothalamo-pituitary-adrenal axis. This study investigates the suite of behavioural and adrenocortical responses to the presence of humans and to handling in two subspecies of blue tits Parus caeruleus, a(More)
Although gene by environment interactions may play a key role in the maintenance of genetic polymorphisms, little is known about the ecological factors involved in these interactions. We investigated whether food supply and parasites can mediate covariation between the degree of adult pheomelanin-based coloration, a heritable trait, and offspring body mass(More)
The specific role of the glucocorticoid hormone corticosterone in regulating the migratory stages of flight and refueling in free-living migrants is as yet poorly studied, because these stages are difficult to identify in the field. Night-migrating songbirds provide an excellent model to investigate how corticosterone correlates with behavior and physiology(More)
Environmental conditions affect growth and development and, through developmental plasticity, create phenotypic variation. In suboptimal conditions current survival is traded-off against development. Corticosterone, the main glucocorticoid in birds, may be involved in the reallocation of energy from growth to maintenance, but its effect on growth has rarely(More)
Elevated baseline corticosterone levels function to mobilize energy in predictable life-history stages, such as bird migration. At the same time, baseline corticosterone has a permissive effect on the accumulation of fat stores (fueling) needed for migratory flight. Most migrants alternate flight bouts with stopovers, during which they replenish the fuel(More)