MACDOUGALL-SHACKLETON, SA*; MACDONALD, IF; KEMPSTER, B; ZANETTE, L; Univ. of Western Ontario; Univ. of Western Ontario; Univ. of Western Ontario; Univ. of Western Ontario: Nutritional stress, brain development and song repertoires in song sparrows

The developmental stress hypothesis posits a mechanism by which birdsong can be maintained as an indicator of male quality. HVC, a brain region critical for learning and production of birdsong, rapidly develops at a time of nutritional stress during the nestling and fledgling stages. Birds best able to withstand this stress should learn to produce the best songs. We tested this hypothesis in song sparrows, Melospiza melodia, a species in which females prefer large song repertoires. Hand reared birds were food restricted or fed ad lib. At 3 weeks of age, food restricted males and females both had reduced size of HVC compared to birds fed ad lib. There was also a large sex difference in HVC size. Food stressed birds also had a smaller telencephalon, but the reduction in HVC size remained significant when the effects of overall reduction in brain size were controlled. Thus, nutritional stress specifically impairs HVC development in both sexes. We also examined the size of HVC in breeding adult males and found it was positively correlated to song repertoire size. Combined, these data support the developmental stress hypothesis as a mechanism by which song repertoires can be an indicator signal in song sparrows.