THE AVIAN SONG OVER TIME: VARIABILITY AND STABILITY

Abstract

Information is reviewed on the dynamics of bird singing over time, analyzing the rate of change in individual and population repertoires, and considering the factors affecting the rate of such changes. The available data indicate very significant periods of persistence of vocal patterns (song types) in songbird populations. The rate of change in population and individual repertoires is higher in species with an unlimited period of imprinting a song compared to species with a fixed period. The population repertoire of song types in numerous populations inhabiting vast and continuous habitats is more stable than in small and isolated populations occupying structurally fragmented habitats. The most common vocal patterns are the most conserved from year to year, while rare variants often disappear from the population repertoire over time. Abnormal climatic phenomena that cause significant changes in the age composition of populations contribute to rapid changes of dialects. The cases of rapid synchronous changes in vocal repertoires in individuals in local populations, as well as in populations separated from each other by a great distance, are considered in detail. The causes that give rise to this need further research. The most likely reasons may be an exchange of vocal models at wintering grounds or the simultaneous introduction of a large number of migrants into the study populations, which in species with an open training period may cause changes in the repertoire of local individuals also borrowing new vocal models.