How long are the vocal sequences a passerine bird can memorize? Common song sequences of Radde’s warbler males (Phylloscopus schwarzi) (Passeriformes, Aves)

Abstract

In most passerine species, an individual bird sings multiple song types to be combined into non-random song sequences. Because of this non-randomness, stereotype sequences of several or even dozens of song types appear in the vocalization of some species. Passerine birds acquire songs through some learning process while imitating other individuals. Song sharing is well known in songbirds and is a consequence of the song learning. Apparently, above the song type level, transitions between song types may be also shared. However, we still do not know exactly, how long are those song sequencies a bird can memorize? We analyze song sequence sharing in Radde’s warbler. Each song of this species consists of a dozen of short notes and lasts 1 s. In many males, the identity of the next song type in a sequence can be predicted on the basis of the previous song type (linear syntax). We found that males can share (i.e. memorize) song sequences from no more than 5 song types. Individual repertoires included up to 40 song types. Therefore, the ability of memorizing song sequences are rather limited in Radde’s warbler, as shared song sequences were rather short in comparison with the total size of the repertoire.