In the new work, the researchers studied songs of the great tit (Parus major), a successful urban-dwelling species, in the center of ten major European cities, including London, Prague, Paris, and Amsterdam. The researchers then compared these songs to those of great tits in nearby forest sites. The results of the comparison showed that for songs important for mate attractions and territory defense, the urban songs were shorter and sung faster than the forest songs. The urban songs also showed an upshift in frequency that is consistent with the need to compete with low-frequency environmental noise, such as traffic noise.
Anthropogenic Impact on Signals Used by Wild Birds
Earlier work, from Dr. Slabbekoorn and another coauthor, had shown that songs of individual birds were adjusted to local traffic noise conditions. The researchers had shown that great tit males in territories with loud low-frequency noise used fewer low-frequency song notes compared to nearby individuals in quieter territories. That single-population study, in Leiden, The Netherlands, included only urban birds, but territory conditions ranged from very quiet to very noisy. The earlier study predicted the possibility that in general, great tits in noisy cities sing higher than great tits in quieter forests: In other words, songs undergo a habitat-dependent acoustic shift in cities that is driven by traffic noise.
With the new findings, Slabbekoorn and den Boer-Visser confirm this prediction and also identify seve