Breeding on top of the world: Environmental regulation of reproduction and the neuroendocrine system in wild song birds.

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 both the timing and the progression of reproduction and associated behaviour. I will give an overview of recent research giving examples from both wild free-living passerines and domesticated species. The change in day length is one key environmental factor used by birds to determine the time of year to migrate and breed. Sex steroids play a key role in regulating reproductive behaviour and neurophysiological studies in zebra finches and Silkie bantam chickens have been particularly useful in elucidating brain mechanisms responsible for behaviours such as nest building, incubation and care of the chicks. Recent investigations into the neural mechanisms underlying complex social and parental care have highlighted the importance of the central mesotocin and vasotocin systems. There is also evidence that neuroendocrine adaptations underlie the unique behaviour required to maximize survival and reproductive success in capricious environments, for example in arctic-breeding passerines such as the socially monogamous white-crowned sparrow, Lapland longspur and the polygynandrous Smith’s longspur. These species rapidly modulate their stress response and adapt their behaviour to optimise reproductive success in a very short breeding season which is often fraught with inclement weather events. Indeed, the white-crowned sparrow is behaviourally insensitive to experimentally elevated testosterone and this insensitivity requires rapid and dynamic changes in the neuroendocrine system. 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 (e.g., the white-crowned sparrow) 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.