Professor Peeter Hõrak, University of Tartu
Anders Pape Møller, PhD, Université Paris-Sud
Physiological ecology studies the interplay of organism's physiological processes and environment. Up until recently, the nervous, endocrine and immunological systems were regarded as separate entities and research about the interconnections and trade-offs between these systems was out of focus. In my thesis I combined immune and stress research with behavioral studies implementing greenfinch (Carduelis chloris) as a research model. Feathers of birds are unique in the sense that various feather parameters can reflect intrinsic and extrinsic conditions experienced by an organism during feather growth. In the first half of my thesis I studied the nexus between neural, endocrine and immunological functions. I asked how stress hormone content of feathers is affected by immune activation, glucocorticoid administration, experimental coccidian infection and how feather corticosterone content relates to disease resistance. In the second half of my thesis I concentrated on the connections between feather parameters and behavior. In the last part, I asked whether feather size and color parameters predict survival in greenfinches facing epidemics of emerging infectious disease, finch trichomonosis. My study showed that morphological characteristics, as well as CORT content of feathers are sensitive to manipulations of hormonal milieu and immune function, which makes these parameters valuable indicators about the events that occurred in the period of feather growth. In particular, feather mass, length and rachis diameter can be used to assess somatic costs of different stressors or trade-offs between feather growth and other demanding organismal functions. Feather wear in captivity can reflect behavior of birds and possibly be linked to stress susceptibility. Fault bars can be used as a diagnostic cue in predicting mortality. My study also indirectly suggests that eumelanotic color of feathers is linked to immune and/or stress responses, which helps us to understand the mechanisms of evolution of melanin-based coloration in general. Detected associations between feather CORT content and resistance to coccidiosis are particularly interesting, as they suggest a novel route of selection for higher stress responsiveness.