Birdsong has a powerful healing effect which can improve mental health and benefit hospital patients, according to a health expert.

Dr William Bird, GP, who is a health adviser for the countryside agency, Natural England, said tests had proven the effect. He cites a 2004 report in the prestigious medical journal, Thorax, on the effects of birdsong on patients recovering from a lung operation. "They needed less pain relief and were far more relaxed," he said.

Dr Bird also recommended birdsong for the elderly and for those who suffer from high levels of stress. "We have lost our connection with nature," he said, adding: "By having birdsong, it's away of connecting back, and our mental health improves when that connection has been made."

Research has found that "ultra waves" increase in the brain when subjects are shown a natural scene, and Dr Bird said the same effect occured with birdsong.

Mark Avery, director of Conservation at the Royal Society for the Protection of Birds, said that bird sounds were a "tonic" for people's general wellbeing.