Behavioral Functions of Vocal Imitation in Parrots

模仿声音在鹦鹉中的行为功能为什么有些动物会模仿复杂的声音？这个问题在鸣禽身上最常见，鸣禽学习歌唱主要是为了保卫领土和/或吸引配偶。然而，这些解释可能不适用于鹦鹉，因为鹦鹉已经独立于鸣禽进化出了非凡的模仿能力。那么，为什么鹦鹉要模仿声音呢？来自Striedter实验室的最新数据表明，鹦鹉的发声学习在配对关系的形成中发挥了作用。具体地说，当雄性和雌性鹦鹉被配对放置时，雄性鹦鹉总是模仿与它们配对的雌性鹦鹉的联系叫声，而雌性鹦鹉则保持原来的叫声。这种模仿行为中的性别不对称表明，男性模仿女性是为了影响女性的配偶选择。如果这一假设是正确的，那么三个预测应该成立：1)性选择应该导致雄性和雌性鹦鹉的发声学习能力不对称。这一假设将通过比较全雄性和全雌性虎皮鹦鹉群体形成共享联系电话的速度来检验。如果男性在发声学习方面“更好”，那么男性的发声收敛应该会比女性更快。2)雄性应优先模仿它们正在追求的雌性。这一假设将通过确定男性学习女性叫声的时间是否与他对女性的兴趣成反比来检验，这一相关性是通过其他众所周知的求爱行为的频率来衡量的。女性的吸引力将通过绘制她的胸部来操纵，成熟女性的胸部是棕色的，而不成熟的女性是淡蓝色的。3)雌性虎皮鹦鹉应该优先与学会模仿它们的雄性虎皮鹦鹉交往。这一假设将通过确定雌性是否会对已经知道自己叫声的陌生雄性(因为他们得到了另一只分享测试雌性叫声的雌性的指导)比对还不知道测试雌性叫声的雄性更多地表现出求爱行为来检验。在一个补充实验中，一些雄性虎皮鹦鹉将通过有选择地切断它们的听觉和声音运动系统之间的连接而导致模仿受损。拟议中的实验可能会对“性选择”和“女性选择”领域产生重大影响，因为之前的大多数研究都集中在女性对公开的身体特征的选择上，而不是学习能力。拟议的实验也为更机械地分析为什么雄性虎皮鹦鹉模仿雌性鹦鹉的叫声铺平了道路。

Behavioral Functions of Vocal Imitation in ParrotsPI: Georg F. Striedterco-PI: Nancy T. BurleyWhy do some animals imitate complex sounds? This question has most frequently been addressed in songbirds, which learn their songs primarily to defend a territory and/or attract a mate. These explanations may not hold for the parrots, however, because parrots have evolved their remarkable imitative abilities independently of the songbirds. So, why do parrots imitate sounds? Recent data from the Striedter laboratory suggest that parrot vocal learning plays a role in pairbond formation. Specifically, when male and female budgerigars are placed in pairs, the males consistently imitate the contact calls of the females with whom they are paired, while the females retain their original calls. This sexual asymmetry in imitative behavior suggests that males imitate females in order to influence female mate choice. If this hypothesis is correct, then three predictions should hold: 1) Sexual selection should have led to an asymmetry in the vocal learning abilities of male and female budgerigars. This hypothesis will be tested by comparing how quickly all-male and all-female groups of budgerigars develop shared contact calls. If males are "better" at vocal learning, then vocal convergence should occur more quickly among males than among females. 2) Males should preferentially imitate females whom they are courting. This hypothesis will be tested by determining whether the time it takes for a male to learn a female's call is inversely correlated with his interest in this female, as measured by the frequency of other, well-known courtship behaviors. The female's attractiveness will be manipulated by painting her cere, which is brown in mature females but pale blue in immature females. 3) Female budgerigars should associate preferentially with males that have learned to imitate them. This hypothesis will be tested by determining whether females give more courtship displays towards unfamiliar males that already know their call (because they were tutored by another female that shares the test female's call) than towards males that do not yet know the test female's call. In a complementary experiment, some male budgerigars will be rendered imitation-impaired by selectively severing the connection between their auditory and vocal motor systems. The proposed experiments could significantly impact the field of "sexual selection" and "female choice" because most prior studies focused on female choice for overt physical traits - not learning ability. The proposed experiments also pave the way for a more mechanistic analysis of why male budgerigars imitate female calls.