Geographic Variations and Temporal Changes in Songs of the Rufous-capped Babbler Stachyris ruficeps praecognita

Abstract

Song has been an important subject in studying geographic variation and cultural evolu-tion across bird populations, but the quantitative analysis of song has been problematic. The aim of this study is to investigate the temporal changes and geographic variations in songs of Rufous-capped Babblers (Stachyris ruficeps praecognita) using both spectro-graphic cross-correlation (SPCC) analysis and multivariate analysis on spectrographic measures. We recorded songs at Shoushan Nature Park of southern Taiwan from 2001 to 2004 and five other sites including Fushan in northern Taiwan, Sun Moon Lake in central Taiwan, and Gauchon, Sanpin, Nazenshan in southern Taiwan. The results showed that the cross-correlation coefficients of songs between bird samples were relatively smaller than those within samples. Using SPCC analysis on first notes instead of whole songs, songs of northern Taiwan could be differentiated from those of central or southern Tai-wan. Results of multivariate analysis on spectrographic measures showed that mean fre-quency, minimum frequency and maximum frequency of the first note were the primary acoustic parameters responsible for this differentiation. However, there were no obvious patterns of temporal changes of songs in the habitat island population of Shoushan Nature Park, which could have resulted from higher variations among individuals within the same year in this high density population. We conclude that the SPCC analysis works as a starting point to examine the geographic variations in songs with simple structures and a following mutivariate analysis is effective in identifying the acoustic parameters resulting in those geographic variations.