DISSERTATION RESEARCH: The Adaptive Benefits to Vocal Mimicry in a Tropical Mixed-Species Flocking Bird

一种热带混种群居鸟声音模仿的适应性益处。鸟类的声音模仿既引起了极大的兴趣，也引起了同样多的挫折，因为研究人员经常无法证明这种行为的适应性好处。虽然人们很容易认为其他物种的模仿会影响这些物种的行为，从而使呼叫者受益，但这一点很少被证明（但参见Chu， Behaviour, 2001）。在古德尔的论文写作过程中，他记录了斯里兰卡热带雨林混合物种群的参与者——大拍尾卷尾龙（Dicrurus paradiseus）的模仿行为。人们观察到，在两种情况下，卷尾鸟会模仿：当它们独处时，它们会模仿其他种群的非警报叫声，而在成群结队时，它们会模仿其他物种的警报叫声。在这项研究中，Goodale将测试模仿功能吸引其他物种的假设，考虑到模仿是增加性选择曲目的一种方式或声音学习的非适应性副产品的替代假设。为了做到这一点，他将a)跟踪和记录群内和群外的卷尾鸟，b)用栖息的鹰模型引起卷尾鸟的反应，c)进行回放试验，测量异种动物对模仿和不模仿卷尾鸟的声音的反应。这项研究可以作为研究这种高度情境依赖行为所涉及的认知过程的基础。这也是本文研究混合种群种间交流的一个合适结论。

The adaptive benefits to vocal mimicry in a tropical mixed-species flocking bird.Avian vocal mimicry has sparked both a great amount of interest and an equal amount of frustration, as researchers have often been unable to demonstrate the adaptive benefits of this behavior. While it is tempting to think that mimicry of other species influences the behavior of these species to benefit the caller, this has rarely been shown (but see Chu, Behaviour, 2001). In the course of Goodale's dissertation work he has documented mimicry by the Greater Racket-tailed Drongo (Dicrurus paradiseus), a participant in mixed-species flocks of rainforest in Sri Lanka. Drongos have been observed to mimic in two contexts: when solitary they mimic the non-alarm vocalizations of other flocking species, and during mobbing they mimic the other species' alarm calls. In this study, Goodale will test the hypothesis that mimicry functions to attract other species, considering the alternate hypotheses that mimicry is a way of increasing a sexually selected repertoire or a non-adaptive by-product of vocal learning. To do this, he will a) track and tape record drongos inside and outside of flocks, b) elicit responses from drongos with models of perched Accipiter hawks, and c) conduct playback trials measuring the response of heterospecifics to drongo mimicked and non-mimicked vocalizations. The study can serve as a foundation to investigate the cognitive processes involved in this highly context-dependent behavior. It is also a fitting conclusion to a dissertation investigating inter-specific communication in mixed-species flocks.