Wild flowers are being planted at five parks across Sutton to create sanctuaries for the dwindling sparrow population.

Areas of Beddington Park, Cheam Park, Perretts Field, Rosehill Park and St Helier Open Space will be turned into meadows over the next three years.

Conservationists have provided £170,000 in funding because London’s house sparrow population has plummeted by 68 per cent in 15 years.

A shortage of insects, due to increased paving and traffic, is thought to be behind the biggest bird mystery of the modern age.

Tim Webb, a spokesman for project managers RSPB, said: “There are some parts of central London where you don’t see sparrows at all any more.

“There has been a dramatic decline and the concern is that the population will reach an unsustainable level and they will disappear completely.”

The conservation scheme is supported by the Sita Trust environmental charity, which handles funds raised through taxes on rubbish sent to landfill.

A total of 20 parks around London are being converted using grass, wildflower meadow and wildlife seed mixes.

In Sutton, an average of 2.84 house sparrows were observed in 600 gardens in 2007, compared with 3.39 three years ago.

A Sutton Council spokesman said: “Knowing whether wildflower meadows, arable land or grass makes the best habitat will inform our choices about how best to support the declining sparrow populations.

“It’s not just sparrows that will benefit – butterflies, bees, bats and all manner of insects will also be attracted to the wild flowers and grasses.”