Inventory size and complexity in the song of the American Robin

Abstract

This paper discusses American Robin morning song and offers a component system to explain its complex structure and discuss the relationship between inventory size and syllable complexity. Previous research has noted that Robin song is combinatorial, meaning Robins are capable of creating different songs by concatenating elements called syllables. For each robin, all unique syllables produced during a 40 minute recording were grouped into a syllable inventory. Inspired by observations linguists have made about human phoneme inventories, a component system was devised that broke each syllable into its smallest parts. These parts were found by using minima in intensity contours to correspond to natural breaks in the robin's utterances. This component system included all unique syllable parts, 7 total, from 11 syllable inventories with between 8 and 24 different syllables. This system showed certain components occurred more often than others and robins with larger syllable inventories had more rare components on average. It also showed each token of the same syllable type had the same component structure. This component system will also be used to test for patterns in sequencing of components in syllable structure to determine where components can occur and constraints on syllable sequencing in overall song structure.