title: Quantifying vocal mimicry in the greater racket-tailed drongo: a comparison of automated methods and human assessment.
abstract: Objective identification and description of mimicked calls is a primary component of any study on avian vocal mimicry but few studies have adopted a quantitative approach. We used spectral feature representations commonly used in human speech analysis in combination with various distance metrics to distinguish between mimicked and non-mimicked calls of the greater racket-tailed drongo, Dicrurus paradiseus and cross-validated the results with human assessment of spectral similarity. We found that the automated method and human subjects performed similarly in terms of the overall number of correct matches of mimicked calls to putative model calls. However, the two methods also misclassified different subsets of calls and we achieved a maximum accuracy of ninety five per cent only when we combined the results of both the methods. This study is the first to use Mel-frequency Cepstral Coefficients and Relative Spectral Amplitude - filtered Linear Predictive Coding coefficients to quantify vocal mimicry. Our findings also suggest that in spite of several advances in automated methods of song analysis, corresponding cross-validation by humans remains essential.
authors.affiliation: Centre for Ecological Sciences, Indian Institute of Science, Bangalore, India.
authors.forename: Samira
authors.initials: S
authors.lastname: Agnihotri
authors.affiliation: Department of Electrical Engineering, Indian Institute of Science, Bangalore, India.
authors.forename: P V D S
authors.initials: PV
authors.lastname: Sundeep
authors.affiliation: Department of Electrical Engineering, Indian Institute of Science, Bangalore, India.
authors.forename: Chandra Sekhar
authors.initials: CS
authors.lastname: Seelamantula
authors.affiliation: Centre for Ecological Sciences, Indian Institute of Science, Bangalore, India.
authors.forename: Rohini
authors.initials: R
authors.lastname: Balakrishnan
mesh_terms: D000465:Algorithms; D000818:Animals; D001307:Auditory Perception / Q000502:physiology*; D006801:Humans; D007100:Imitative Behavior / Q000502:physiology*; D046109:Passeriformes / Q000502:physiology*; D012815:Signal Processing, Computer-Assisted; D013018:Sound Spectrography / Q000379:methods; D013045:Species Specificity; D014828:Vocalization, Animal / Q000502:physiology*