Songbirds suffer from competing with noise

ST. ANDREWS, Scotland, June 29 (UPI) -- Songbirds trying to compete with city noise are damaging themselves and possibly leaving their offspring a poorer genetic inheritance, European researchers say.

Sue Anne Zollinger of the University of St. Andrew's said the effect of traffic and other noise is so great that birds living in the city and their country cousins may no longer be able to use their songs to communicate with each other, The Observer reported. That reduces the potential gene pool for both birds.

Urban birds tend to increase their volume and use higher frequencies. One study found nightingales in Berlin sing 14 decibels louder than those in rural areas.

"All this effort puts the same strain on a bird's vocal cords as when a human tries to shout to be heard in a noisy pub -- except the birds are doing it all day, every day," she said.

Henrik Brumm of the Max Planck Institute of Ornithology in Germany said rural and urban populations may evolve into separate species. He said some existing species appear to lack the flexibility to adapt, so overall population numbers drop.