Song of the snow bunting (Plectrophenax nivalis) in areas with and without sympatric passerines

摘要

The acoustic-competition hypothesis predicts that in areas with low species diversity, bird song will vary more from one individual to another and the song of each individual will be less complex than those of conspecifics in areas with more species. The aim of this study was to investigate whether this prediction also applies to the snow bunting (Plectrophenax nivalis), which is the only passerine species that breeds regularly in Svalbard, whereas on the Scandinavian mainland it breeds sympatrically with several other species. Songs of 22 and 19 male snow buntings from study areas at Longyearbyen in Svalbard and on the Varanger peninsula in northern Norway, respectively, were analysed with respect to the number and type of syllables and motifs, syllable and intersong diversity, song length, maximum, minimum, and range of frequency, and sharing of song features between individuals. None of the variables diffcied significantly between the two areas with respect to song variation between individuals. It is suggested that this is related primarily to the migratory and vagrant behaviour of the species, which is thought to entail a considerable annual turnover in the breeding populations in relation to the geographical origin of the birds. Songs were significantly simpler in Svalbard than on tire mainland only when complexity was measured as syllable diversity. When it was measured in terms of diversity of song motifs, an opposite, although insignificant, trend was found. The reason for this contradictory tendency ix discussed in relation to the problem of defining complexity and choosing relevant variables for assessing song complexity. Individuals in both areas commonly shared syllables, but rarely motifs and song types. The snow buntings in Svalbard shared song features to about the same extent as the birds on the mainland.