Barry White knew it, and male Great Tits know it too: to be successful with the ladies you have to sing as low as possible. But to be heard above city noise, you need to sing high notes. Leiden biologist Wouter Halfwerk studies the role of pitch in communication between city birds.
The results of his research have been published in PNAS.
Halfwerk and his colleagues from the Behavioural Biology research group at the Institute of Biology in Leiden discovered that male Great Tits sing at much lower pitch when the females of the species are at their most fertile. The male that achieves the lowest notes is most successful with the females. Female Great Tits actually cheat on their mate if he does not manage to sing low enough.
Male Great Tits, as well as other male birds found in the city, are faced with a dilemma: how can they make sure they are heard above the noise of people and traffic? Results from earlier research suggest that they can achieve this by singing their songs at higher pitch. Measurements taken by the Institute of Biology Leiden show that this is an effective approach for being heard better, but the downside is that females find these songs less impressive. Females have a definite preference for lower notes.
Need to distinguish themselves
The researchers predict that city birds will therefore switch to other acoustic characteristics to distinguish themselves from competing males. The research results show that bird species that rely on low notes to attract partners, suffer most from the effects of city noise. This explains why these species breed less in areas close to mail roads than species that inhabit more peaceful locations.
- W. Halfwerk, S. Bot, J. Buikx, M. van der Velde, J. Komdeur, C. ten Cate, H. Slabbekoorn. Low-frequency songs lose their potency in noisy urban conditions. Proceedings of the National Academy of Sciences, 2011; 108 (35): 14549 DOI: 10.1073/pnas.1109091108
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