Technogenic Noise Affects the Minimum Frequency of Chaffinch Song Components (Fringilla coelebs) in the Moscow Population

Resumo

To test the hypothesis that birds shift song parameters to higher frequencies in response to continuous low-frequency noise, we received records of vocalizations from 78 male chaffinchs in Moscow city parks. The levels of noise were recorded for each recording point. Based on phonograms, we measured the minimum frequency of four phrases in three common songs types in Moscow. Measurements of each phrase were made in 18–21 males with measurement of four songs of a given type in each male, which were randomly selected from a phonogram. The minimum frequency in the vocalizations of various males varied from 4.94 to 5.22 kHz for phrase 1, from 2.23 to 2.6 kHz for phrase 2, from 1.77 to 2.64 kHz for phrase 3, and from 2.08 to 2.42 kHz for phrase 4. A significant positive correlation (the Pearson correlation coefficient, 0.67 < r < 0.79) of the minimum frequency with the noise level was revealed for three out of the four phrases studied. A sharp increase in the minimum frequency of singing with increased noise was revealed at a noise level of 55 dB and above.