Logan C A, Wingfield J C
Department of Psychology, University of North Carolina, Greensboro 27412.
Horm Behav. 1990 Dec;24(4):568-81. doi: 10.1016/0018-506x(90)90042-v.
Mockingbirds (Mimus polyglottos) show intense territorial activity in the autumn as newcomers attempt to establish space within resident populations. Examination of autumnal territorial behavior showed that unmated males sing more and engage in more territorial fights than mated males. Newcomers that have just acquired space also sing more and show more territorial fights than birds resident to the population for at least one prior season. Among established residents, the average number of territorial fights was greater in birds that shared more territory boundaries with new residents. Radioimmunoassay of plasma samples taken from males during the molt and following the onset of territorial defense showed that during both periods plasma concentrations of testosterone (T), dihydrotestosterone (DHT), and estradiol were basal or below the sensitivity of the assay system. Moreover, groups of males that differed in song and territorial aggression did not differ in plasma concentrations of T, DHT, or luteinizing hormone (LH). Hormone analyses confirm measurements on several other avian species suggesting that sex steroid concentrations are low in the fall and winter and that variations in aggressive behavior at this time of year may be unrelated to LH and androgen levels. Our observations contribute to a growing body of work in temperate passerines indicating that the role of androgens in mediating aggressive challenge may be restricted to the breeding season. The possible hormonal basis (if any) of song and territorial aggression in mockingbirds outside the breeding season remains obscure.
模仿鸟（美洲知更鸟）在秋季表现出强烈的领地行为，因为新鸟试图在留鸟群体中占据空间。对秋季领地行为的研究表明，未交配的雄性比已交配的雄性唱歌更多，参与的领地争斗也更多。刚获得领地的新鸟也比至少在前一个季节就已定居的鸟唱歌更多，表现出更多的领地争斗。在已定居的留鸟中，与新居民共享更多领地边界的鸟，其平均领地争斗次数更多。对雄性在换羽期和开始进行领地防御后采集的血浆样本进行放射免疫分析表明，在这两个时期，睾酮（T）、双氢睾酮（DHT）和雌二醇的血浆浓度均处于基础水平或低于检测系统的灵敏度。此外，在唱歌和领地攻击性方面存在差异的雄性群体，其T、DHT或促黄体生成素（LH）的血浆浓度并无差异。激素分析证实了对其他几种鸟类的测量结果，表明秋季和冬季的性类固醇浓度较低，而且每年这个时候攻击行为的变化可能与LH和雄激素水平无关。我们的观察结果为温带鸣禽中越来越多的研究工作做出了贡献，表明雄激素在介导攻击性挑战中的作用可能仅限于繁殖季节。繁殖季节外模仿鸟唱歌和领地攻击行为可能的激素基础（如果有的话）仍然不清楚。
