Meeting Abstract

65.4  Monday, Jan. 6 09:30  Behavioural neuroendocrinology in free-living wild Arctic breeding song birds: tales from the tundra… MEDDLE, SL; The Roslin Institutte, University of Edinburgh simone.meddle@roslin.ed.ac.uk

Investigations into the neural mechanisms underlying complex male aggressive and reproductive behaviour in free-living wild birds are important as they provide a necessary compliment to captive studies; particularly since the context-dependency of complex behaviours is now recognized. We now have evidence that neuroendocrine adaptations underlie the unique behaviour required to maximize survival and reproductive success. Arctic-breeding birds, such as the white-crowned sparrow (Zonotrichia leucophrys gambelli) and Smith’s Longspur (Calcarius pictus), adapt their behaviour to optimise reproductive success in a very short breeding season. The males of these species are behaviourally insensitive to experimentally elevated testosterone (T) and the stress hormone corticosterone (CORT) after courtship has terminated. Unlike most temperate species, which show heightened aggression when given T implants, these Arctic breeding male passerines appear to become non-responsive to T. This refractoriness is thought to be an adaptation to the short breeding season experienced at high latitudes and this insensitivity must require rapid and dynamic changes in the neuroendocrine system. Studies quantifying changes in the expression of aromatase, androgen and oestrogen receptors in the white-crowned sparrow brain have revealed that oestrogen-dependent rapid transitions in aggressive behaviour are mediated by differences in neural oestrogen synthesis. A lower latitude breeding song bird, the song sparrow (Melospiza melodia morphna), also demonstrates changes in aromatase expression in specific brain regions throughout the year suggesting that seasonal aggression is regulated by an oestrogen-dependent mechanism in other avian species too.