Experimental evidence that distinct song phrases in the Grey-cheeked Fulvetta Alcippe morrisonia permit species and local dialect recognition

Birds with small song repertoires have a limited number of song types which may serve multiple functions. The Grey-cheeked Fulvetta Alcippe morrisonia is a non-migratory species of lowland forests in Taiwan. Its song consists of two distinct phrases: a whistled phrase and a harmonic one. Each individual usually sings only one type of whistled phrase, and the geographical patterns of songs can be distinguished by the motif of this phrase. We proposed a dual adaptation hypothesis for the functions of these two phrases. Playback experiments including six sound stimuli (familiar whistled phrases, familiar harmonic phrases familiar complete songs, foreign whistled phrases, foreign harmonic phrases and foreign complete songs) were conducted at 12 sites in the Shoushan Nature Park of Kaohsiung, Taiwan. Grey-cheeked Fulvettas came closer to the playback speaker and increased counter-singing more in response to the familiar whistled phrase (local dialect) than to a foreign whistled phrase (distant dialect). However, birds responded equally to the playback of harmonic stimuli from familiar and foreign sources. We suggest that in this species, whistled phrases are used for local recognition and harmonic phrases are used for species recognition in short-range communication.