Prof Simone Meddle

For most bird species reproduction is seasonal and breeding is regulated by environmental cues including photoperiod, food availability, temperature and social interactions. My research interests lie in understanding how these environmental factors coordinate the both the timing and the progression of reproduction and associated behaviour.  I will give an overview of recent research giving examples from wild free living passerines. The change in day length is one key environmental factor used by birds to determine the time of year to breed.  Birds use extra retinal photoreceptors and their circadian system to interpret the light:dark signal. Gonadal development is under the control of gonadotrophin secretion from the pituitary gland and under increasing day lengths thyrotrophin triggers a flow of molecular events in the mediobasal hypothalamus to increase the synthesis of triiodothyronine which ultimately leads to gonadotrophin releasing hormone synthesis and release until photorefractoriness.  Nonetheless there is inherent flexibility for precisely when birds transition from their reproductive states. Recent investigations have highlighted the importance of steroids in the regulation of the HPA axis and in response to acute environmental perturbations. These adaptations underlie the unique behaviour required to maximize survival and reproductive success in capricious environments, e.g. in arctic-breeding passerines like the socially monogamous white-crowned sparrow.  This species rapidly modulates its stress response and adapts behaviour to optimise reproductive success in a very short breeding season which is often fraught with inclement weather events. With such wonderful examples of environmental adaptations and regulation, avian behavioural neuroendocrinologists are entering an exciting period. Using the annotation of many more avian species genomes to devise comparative genomic approaches and species-specific genetic tools, the identification of the genes responsible for integrating environmental information, neuroendocrine signals and reproductive behaviour is within our reach.