Evolving tunes: temporal shifts in the Great Reed Warbler dialects

In some bird species, geographic variability in song results in different populations exhibiting unique vocalization characteristics, a phenomenon referred to as dialects. Dialects can arise as a byproduct of factors such as the accumulation of errors during song learning in isolated populations. Alternatively, they may have adaptive significance, for instance, enabling females to recognize philopatric males or allowing males to channel territorial aggression into conventional communication. One relatively unexplored aspect of dialects is their temporal stability, as such studies often require long-term monitoring of the same population, which can be challenging or even infeasible. The aim of this study is to determine whether the characteristic dialect of a given population of Great Reed Warblers Acrocephalus arundinaceus is maintained across generations. Changes in vocalizations over time were investigated by comparing the songs of the same Great Reed Warbler population recorded over a time span encompassing several consecutive generations. The analyses revealed weak dialect stability over time. After 12 years, differences in syllable composition within the same population were comparable to those observed between geographically distant populations, indicating a low copy fidelity. Furthermore, some syllables previously associated with harem size and polygyny disappeared from the songs of subsequent generations.