Sforzi canori

C’è un problema di fondo che deriva dall’inquinamento acustico: in zone molto rumorose a causa del traffico, della presenza di industrie o di altre fonti rumorose le cinciallegre maschio inizano a cantare con tonalità più alte, per farsi sentire dalle femmine. Ma queste ultime preferiscono i toni più melodiosi e non quelli più alti.

Così si arriva a un compromesso evolutivo, perchè chi ha un canto più attraente rischia di non essere sentito rispetto ai maschi con una melodia meno piacevole ma capace di sovrastare il rumore. Sacrificare il bel canto almeno per trovarsi.

Noise pollution from roads, industries and other sources forces some birds to sing at higher frequencies.

By changing their tunes, male birds become less attractive to females.

Noise is just one of many threats facing birds around the world.

When bombarded by noise pollution, some male birds begin to sing higher tunes, found a new study. And that tonal shift makes them less attractive to females.

The findings suggest that birds must make difficult trade-offs in urban areas and places where traffic and industrial noises threaten to drown them out. Either they sing less appealing songs or tones in an effort to rise above the din, or they sing the songs that make them sound appealing at the risk of not being heard at all.

“If females can hear all song types equally well, they will go for the sexy ones, but if they cannot hear the sexy ones well anymore, then they might just go for the songs they can still hear,” said Wouter Halfwerk, a behavioral ecologist at Leiden University in the Netherlands. “It could very well be that noise pollution is interfering with reproductive decisions by females.”

Read more

via Birds Are Changing Their Tune – Emily Sohn – Discovery News – RichardDawkins.net.

Annunci