Urban noise forced tits sing tenor, bass, and not – scientists

Background noise interferes with urban birds during the breeding season to find a partner – they just can not hear each other singing in the noise of cars and factories. To cope, many kinds of urban birds have raised the height of his singing, because the noise drowns out less high-frequency sounds. Many biologists believe that this form of adaptation to new environmental conditions can affect the sexual behavior of birds. A team led by Wouter Halfverka (Wouter Halfwerk) from the University of Leiden (the Netherlands) found that in the wild, males and females of tits (Parus major) use low-frequency trills to demonstrate their readiness to mate and to attract partners. Typically, the duration and the "recognition" of the male songs allow him to express their strength, personality and adaptability to environmental conditions. "Poor performance" songs can tell the females that one or another male is not very well – we know that the quality of the songs directly affect parasites and diseases. Halfverk and his colleagues have constructed and hung on trees in the forest a few special birdhouses, inside and outside of which were hidden microphones by which scientists recorded the singing of tits. The researchers found that males lowered the height of his "Serenade" in the days before laying eggs. To respond females who responded to the calls of males of birdhouses and after a while let them inside. As they note, its fidelity to the female "gentleman" – that is, incubation and feeding chicks – depended on the length of the song, but no matter how "low" was his trill. Scientists examined how females respond to male song writing, which had been stifled noise of the highway, at a distance of 50 and 100 meters from the nest. To do this, biologists have imposed on the recording of singing male tits artificial road buzz created by a computer program. The researchers then consolidated on the roof birdhouse box with a speaker, with which they imitated the singing males. The experiment showed that the high trills evoked more sympathy in females compared with low-frequency song, which has lost its effectiveness due to merge with the background noise. The article notes that these males tits are adapting to the emergence of urban noise, increasing the height of their trills. Biologists believed this leads to a decrease in "repertoire" of males, which limits the effectiveness of natural selection.