University of Antwerp, Research Group of Ethology, Wilrijk, Belgium.
Horm Behav. 2012 Nov;62(5):563-8. doi: 10.1016/j.yhbeh.2012.09.008. Epub 2012 Oct 1.
Song in songbirds is a learned secondary sexual behavior, first acquired during a sensitive phase of juvenile development, which is affected by hormones such as testosterone (T). While the latter has received much attention, the potential involvement of T in the adult repertoire changes observed in a number of species is much less understood. Yet, this may prove essential to understand the role of song as a sexually selected trait. We therefore performed a T-implantation experiment during the non-breeding season (when T is basal), using adult male European starlings (Sturnus vulgaris), a songbird species in which song repertoire size (and composition) changes seasonally and increases with age. Repertoire size increased rapidly in T-males, but not in control males, indicating a role for T in repertoire size changes. This increase resulted from a lower proportion of dropped song types in T-males than in control males, while the proportion of added song types did not differ between both groups. Interestingly, the observed repertoire turnover (adding and removing song types from the repertoire) in both groups, suggests that elevated plasma T levels were not essential for changes in repertoire composition (contrary to repertoire size). Finally, T-males (but not control males) significantly increased their song rate, while neither group showed a significant change in their song bout length and phrase repetition rate. Taken together, our results suggest a role for T in adult song learning and provide new insights into the information content of repertoire size and song bout length as sexually selected traits.
鸣禽的鸣唱是一种后天习得的次要性行为，最初是在幼年发育的敏感阶段获得的，这一阶段受到睾酮（T）等激素的影响。尽管后者受到了广泛关注，但 T 对许多物种成年期行为变化的潜在影响却鲜为人知。然而，这对于理解鸣唱作为一种性选择特征的作用可能至关重要。因此，我们在非繁殖季节（T 处于基础水平时）对成年雄性欧洲椋鸟（Sturnus vulgaris）进行了 T 植入实验。在这种鸣禽中，鸣唱曲目大小（和组成）会季节性变化，并随年龄增长而增加。T 处理的雄性鸣唱曲目大小迅速增加，但对照雄性没有增加，这表明 T 在鸣唱曲目大小变化中起作用。这种增加是由于 T 处理雄性中被丢弃的鸣唱类型比例较低，而两组之间添加的鸣唱类型比例没有差异。有趣的是，两组观察到的鸣唱曲目更替（从鸣唱曲目添加和删除鸣唱类型）表明，升高的血浆 T 水平对于鸣唱曲目组成的变化并非必需（与鸣唱曲目大小相反）。最后，T 处理的雄性（而非对照雄性）显著增加了它们的鸣唱率，而两组在鸣唱片段长度和短语重复率方面都没有显著变化。综上所述，我们的结果表明 T 在成年鸣唱学习中起作用，并为鸣唱曲目大小和鸣唱片段长度作为性选择特征的信息内容提供了新的见解。
