Thousands of householders are being urged to redesign their gardens to halt the rapid decline of sparrows and starlings. Conservationists believe that bird numbers could be boosted by 20 per cent if 200,000 people let their gardens grow wild and planted insect-friendly flowers and shrubs.

The number of common garden birds has dropped significantly over the past 35 years – house sparrows by 64 per cent, starlings 72 per cent and song thrushes 50 per cent. The RSPB believes that one of the reasons is the scarcity of food for chicks.

The RSPB’s Homes for Wildlife project, which begins on Saturday, offers detailed advice on how to increase biodiversity in gardens. Most of it centres on making gardens more attractive to insects, the birds’ main source of food. This includes:

— Let patches of lawn grow long to provide shelter for insects

— Stack pruned twigs and branches at the base of trees to encourage fungi, mosses and lichens

— Plant flowers and shrubs that are rich in nectar and seeds, such as knapweeds, sunflowers and cranesbills

— Plant native trees instead of foreign species to attract native insects

— Create curved borders to increase the length of the garden’s edge

— Grow climbers at the back and sides of garden sheds.

Richard Bashford, the project’s manager, said that even those without gardens could make their homes more friendly for wildlife. “If everybody does something for wildlife, it will make a difference – from putting pot plants on balconies to building a pond, you will encourage insects and provide food for birds. We can all create homes for wildlife in our own homes, no matter how much space we have.”

He said that holes could be dug into hard-standings and filled with compost and soil to promote the growth of vegetation. Pot plants with nectar-rich flowers could also be placed on balconies, patios and roof gardens.

Darren Moorcroft, head of the RSPB conservation advice team, said that people should start thinking about giving homes a green make-over at the design stage. This was especially important in light of the Government’s plans to build three million new homes by 2020. One such change would be to incorporate nesting areas into roofs for new houses.

Mr Moorcroft said: “As more land is developed to provide homes for people, this could remove homes for wildlife. Metre for metre, gardens are the richest wildlife habitat on Earth and every garden is part of a much bigger community.”

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