title: Temporal regularity increases with repertoire complexity in the Australian pied butcherbird's song.
abstract: Music maintains a characteristic balance between repetition and novelty. Here, we report a similar balance in singing performances of free-living Australian pied butcherbirds. Their songs include many phrase types. The more phrase types in a bird's repertoire, the more diverse the singing performance can be. However, without sufficient temporal organization, avian listeners may find diverse singing performances difficult to perceive and memorize. We tested for a correlation between the complexity of song repertoire and the temporal regularity of singing performance. We found that different phrase types often share motifs (notes or stereotyped groups of notes). These shared motifs reappeared in strikingly regular temporal intervals across different phrase types, over hundreds of phrases produced without interruption by each bird. We developed a statistical estimate to quantify the degree to which phrase transition structure is optimized for maximizing the regularity of shared motifs. We found that transition probabilities between phrase types tend to maximize regularity in the repetition of shared motifs, but only in birds of high repertoire complexity. Conversely, in birds of low repertoire complexity, shared motifs were produced with less regularity. The strong correlation between repertoire complexity and motif regularity suggests that birds possess a mechanism that regulates the temporal placement of shared motifs in a manner that takes repertoire complexity into account. We discuss alternative musical, mechanistic and ecological explanations to this effect.
authors.affiliation: Department of Psychology , Hunter College, CUNY , New York, NY , USA.
authors.forename: Eathan
authors.identifier: 0000-0001-6788-614X
authors.initials: E
authors.lastname: Janney
authors.affiliation: Macquarie University , Sydney , Australia.
authors.forename: Hollis
authors.initials: H
authors.lastname: Taylor
authors.affiliation: Freie Universität, Berlin; Institute of Biology , Berlin , Germany.
authors.forename: Constance
authors.initials: C
authors.lastname: Scharff
authors.affiliation: Department of Humanities , New Jersey Institute of Technology , Newark, NJ , USA.
authors.forename: David
authors.initials: D
authors.lastname: Rothenberg
authors.affiliation: Department of Biomedical Engineering , City College of New York, CUNY , New York, NY , USA.
authors.forename: Lucas C
authors.initials: LC
authors.lastname: Parra
authors.affiliation: Department of Psychology , Hunter College, CUNY , New York, NY , USA.
authors.forename: Ofer
authors.initials: O
authors.lastname: Tchernichovski
keywords: aesthetic balance; birdsong; butcherbird; complexity; music; temporal regularity