Phenotypic flexibility, physiological tradeoffs and performance in wintering and migratory birds

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The aim of this program is to understand how animals facing high energy demands, while constrained by body design and energy supply, adjust their physiological systems to solve conflicting demands and maximize survival and reproduction. We work with two bird species that routinely encounter extreme physiological constraints likely to shed light on consequences of those adjustments: resident black-capped chickadees and a long-distance migratory shorebird, the red knot. Our three short-term objectives are (A) to investigate long-term consequences of physiological trade-offs in birds facing conflicting constraints during winter and migration, (B) to quantify the speed of adaptive change and range of flexibility in physiological traits in order to examine how trait flexibility may constrain life-histories and (C) to investigate hormonal regulation of cold acclimatization in birds. Combining experimental studies in captive and free-living conditions, we are studying animal's responses to environmental variations from the cell level to the whole animal and population. My program involves two local projects (chickadees) as well as two projects to be carried out in four European countries (red knots, France, Netherlands, Iceland and Norway). We will study: (1) the role of thyroid hormones in regulating the metabolic response to cold and winter improvement of cold endurance; (2) how winter climatic conditions and energy expenditure interact with habitat quality in influencing metabolic performance, physiological condition, survival and reproduction; (3) how amplitude and speed of physiological trait adjustments affect survival in wintering knots facing conflicting demands for digestion and thermoregulation and; (4) how amplitude and speed of adjustments might limit migration pace and individual condition in knots facing extreme physiological demands during migratory stopover. Our findings will be of major importance, as they will provide an integrated understanding of the interplay between ecological and physiological constraints in shaping animal's adaptive response to their environment. Results will help us understand how organisms adjust their physiology to rapid environmental alterations and climate change.