Song variation and the structure of local song dialects in the polygynandrous Smith's Longspur

Abstract

I examined song structure in five populations (or neighbourhoods) of the polygynandrous Smith's Longspur (Calcarius pictus) near Churchill, Manitoba, Canada, from 1988 to 1994. All after-second-year (ASY) males sang only a single song type. This song type did not vary within ASY males over the season or from year to year and it was nearly identical among all ASY males within a neighbourhood. However, the song type of ASY males differed significantly from one neighbourhood to the next in the number of elements, total length (s), and minimum frequency (kHz). Neighbourhood dialects were readily distinguishable by the human ear and, except in one case, persisted over the duration of the study. In contrast to the uniformity of ASY male song within a neighbourhood, the song of second-year (SY) males did not match the local dialect. Only when SY males returned for a second year did their song and the neighbourhood dialect of ASY males converge. There were no differences in song structure that could be related to the complex mating system of this species. The function of neighbourhood dialects is not clear, but they may be used by both males and females as a signal of affiliation and experience with the local area.