How does environmental stress modulate migratory strategies?
Birds have evolved remarkable phenotypic flexibility to accommodate the demands of migration. In preparation to migratory flights birds show physiological and behavioural changes that lead to increased food intake and fat stores. Once they have accumulated sufficient energy reserves, several bird species also invert their daily rhythms and show maximal locomotor activity at night - termed nocturnal migratory restlessness in captive birds. To date, the internal mechanisms regulating such phenotypic flexibility are largely unknown. Studies suggest that early life nutritional stress can influence the amount and rate of migratory fattening with consequences for survival during the later migratory stages. Glucocorticoid stress hormones are key mediators of responses to stressors, such as food shortages or inclement weather conditions, and are well known regulators of energy mobilisation influencing appetite and locomotor activity. We aim to test if exposure to environmental stress - in form of unpredictable shortages of food - across differing pre-migratory life stages influence fattening dynamics and the onset of nocturnal restlessness behaviour. We will use our recently established captive population of common quail (Coturnix coturnix) as a study species. We will perform longitudinal experiments to obtain repeated within-individual measurements of circulating levels of appetite- and stress-regulating hormones (ghrelin and corticosterone). In addition, we will quantify expression of orexigenic and anorexigenic genes in the brain to assess whether key neuroendocrine and endocrine factors regulating energy metabolism mediate any effects of exposure to environmental stress on the recorded migratory behaviours. Finally, we will perform experimental manipulations to test whether the effects linked to exposure to environmental stress are mediated by the action of glucocorticoids. The project has several innovative aspects: (1) we will perform experiments in controlled laboratory conditions without the need of taking wild birds; (2) we will track the same individual birds since early stages of life to monitor of the dynamics of the development and expression of the migratory phenotype, and (3) we will use multi-disciplinary approaches to study molecular, physiological, and behavioural variables in the same individual birds thus reducing the number of animals required. Understanding the mechanisms behind the remarkable phenotypic flexibility shown by a migratory Galliform will provide insights that can be directly translated to poultry science and fields of biomedical research focused on nutrition.
Wie beeinflusst umweltstress migrationsstrategien?