The disagreement in results with previous studies can be due to variation in song repertoire learning LY2109761 programmes between the studied populations or by differences in methodological approaches between the studies. Previous research has shown that populations of the same species may differ in song learning programmes. For instance two different populations of the great reed warbler located in Germany and Sweden have been found to differ in learning strategies. Individuals from the Swedish population increased repertoire size with age while this was not the case in the German population. Previous studies on the great tit have also reported differences of song traits at the population level. For instance, the maximum frequency and the average number of notes per song type vary among different populations. Moreover,great tits from nearby forest and city populations seem to differ in frequency and time parameters. This could indicate that repertoire flexibility may be linked to particular populations and conditions. However, because differences in repertoire plasticity and learning programmes among populations have not been studied in detail, the possibility that different populations of the same species may develop a different song learning programme may have been overlooked. As a result, there is no evidence at present that repertoire plasticity is a population-related trait. On the other hand, population dynamics also seem to play an important role in repertoire composition at population level. Different aspects such as recruitment rate, age structure or number of immigrant birds may have an impact on the song repertoires in the population. However, it still remains unclear whether this could have an impact on the learning programmes. Alternatively, another explanation is that differences in methodological approaches among studies may have affected the assessment of repertoire size and composition, and, as such, also the assessment of repertoire plasticity. Unlike Franco & Slabbekoorn, we used a colour-ringed nest box breeding population, which enabled us to individually identify the males during all phases of the experiment. As territorial interactions occur every day, birds may move or change singing perches, and territorial take-overs are possible. Consequently, misidentification may occur and may become a confounding factor. In addition, given that previous studies have shown that focal birds respond less aggressively if the simulated intruder during a playback is located outside the territory, the playback stimulus in our experiment was placed at a standardized distance from the nest box. Moreover, unlike the two previous studies, we tried to employ a standardized recording method taking into account the ‘song ecology’ of great tits. We only recorded complete dawn choruses during egg laying, and the complete playback experiment was performed during this reproductive stage, which is the period of peak singing activity in the great tits.