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“ Forum:"Structural design principles of a complex birdsong" ”

BSI Private Event

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June 09, 2010 15:00 - 16:00


Birdsong is an acoustic signal primarily used in male-male aggression and in male-female attraction. Some songbirds, such as the Brown Thrasher and the Sage Thrasher, have extremely complex song consisting of hundreds or thousands of different syllable-types. Revealing the structural design principles of such complex song is an important step toward better understanding the evolution of animal communication systems, yet little is known about them. Previous studies have focused primarily on repertoire size (the number of different syllable-types) as a measure of song complexity, rather than song structure (the organization of syllables). One obvious fact is that the diverse syllable-types are arranged in sequences that are neither uniform nor random, but with some intermediate and discernible pattern. Here we illustrate structural design principles underlying complex birdsongs via two types of network analysis of California Thrasher songs. We find that the song network―the transition relationships among different syllable-types―has a ‘small-world’ architecture, wherein many groups of syllable-types are sparsely connected. This network also exhibits a balanced-coexistence of deterministic and non-deterministic transitions, guided by a simple rule: ‘the popular syllable-types show more diverse transitions.’ Furthermore, it appears that the dynamics of the song network can be attributed to a simple context-dependent process, a first-order Markov chain. Our findings indicate that the songs of this species are highly structured, with rules that are likely shaped by both learning and evolution, to effectively produce the signal complexity that is a key factor in animal communication.

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BSI Private Event
Kazuo Okanoya