Nesting-box makeovers are needed to entice struggling house sparrows

Once they were the outcasts of the avian world. Now house sparrows are finding that wheels are turning and doors are being opened to welcome them back.

Not doors, exactly, but nest-box entrance holes, which are being enlarged to entice them. For such are the fallen fortunes of what was once Britain's commonest and most familiar bird – highlighted for nearly two years by The Independent – that National Nest Box Week, in a month's time, has a house-sparrow theme in 2002. The annual event, organised by the British Trust for Ornithology (BTO), is being dedicated to house sparrows and to ways of encouraging them to rear their families in such purpose-built structures.

Yet little more than a generation has passed since people were being advised to put up nest boxes specifically designed to keep out the house sparrows and to draw in more colourful species.

When interest in attracting birds to gardens began mushrooming in the 1960s, nest-box construction advice usually included the tip that the entrance hole should be made small enough to exclude what was then one of the most abundant birds in Britain.

The old attitude was typified in the section on nest-box building in The Book of Bird-Watching by R M Lockley in 1968. Attracting blue tits, smaller and more colourful, was the main aim. He wrote: "Probably you will think your local starlings and sparrows, if plentiful, are able to find plenty of nest holes for themselves.

"If you want tits, the hole should not be more than one-and-an-eighth-inch [2.9cm] in diameter."

Chris Mead of the BTO, the man behind Nest Box Week, recalls one-and-a-sixteenth-inch diameter as being an even more certain guarantee of positive discrimination in favour of blue tits. If the hole was just three-sixteenths of an inch wider a house sparrow would be able to squeeze inside.

However, this year the one-and-a-quarter-inch minimum will be in vogue, to allow vanishing sparrows house room – when they can be found.

"Not long ago the house sparrow was one of urban Britain's commonest nesting birds," Mr Mead said. "However, numbers have declined by 43 per cent since 1968 and in some areas the species has become rare." They have notably almost vanished from several city centres that used to be strongholds, such as London.

Jeff Baker, the BTO co- organiser, added: "While we still don't know what has caused the decline, house sparrows choosing to nest in boxes will at least improve the survival chances of their young. In my youth when we put up nest boxes, the main aim was to keep sparrows out of them – I never imagined the day would come when I'd be encouraging a totally opposite policy."

The BTO has produced hint sheets with details on house sparrows and box building. These will be available through the BTO website, www.bto.org

* The Independent continues to offer a £5,000 prize for the first paper published in a reputable peer-reviewed scientific journal which, in the opinion of our referees, offers a convincing explanation for the disappearance of the house sparrow from British towns and cities.