Many popular British garden birds have seen their fortunes improve over the last few years, a survey reveals.
By Alex Kirby
BBC News Online environment correspondent
The 2002 breeding bird survey collected information on birds throughout the UK.
Cuckoo: Sound of spring less heard
Of the 105 species monitored across the country, 29 had declined significantly since 1994, but 52 had registered significant increases.
The government uses changes in breeding birds' status as an indicator of the UK's sustainable development.
The survey, which began in 1994, is carried out by the British Trust for Ornithology, the Joint Nature Conservation Committee, and the Royal Society for the Protection of Birds.
Volunteer birdwatchers are given randomly-selected one-kilometre squares to visit three times in the season. Each of them spends about two hours early in the day counting all the birds they see and hear.
In 2002, a total of 2,136 sites were surveyed across the UK by more than 1,700 volunteers.
Blue tit: On the up
Of the 18 most commonly-encountered birds across the whole of the UK, 14 showed an increase in numbers between 1994 and 2002.
They are (in descending order of frequency) the woodpigeon, chaffinch, blackbird, wren, robin, crow, blue tit, great tit, dunnock, swallow, magpie, song thrush, greenfinch and pheasant.
The four which declined were the starling, skylark, house sparrow and willow warbler.
Other less common species showed mixed fortunes, with both kingfishers and great spotted woodpeckers, for example, increasing by more than 50%, but wood warblers and willow tits decreasing by the same amount.
Three "red-listed" species, targeted for conservation action, have increased significantly: the song thrush, marsh tit and tree sparrow.
London sparrows have plummeted
But 16 species described as widespread have been placed on the red list because of long-term population trends.
The survey organisers say their most worrying finding is probably the decline of the willow tit, whose numbers fell by 72%.
They are also concerned about the large decline in south-east England of the house sparrow, down by 28% across the region and by 71% in London.
Yet in some other parts of England sparrow numbers are stable or even increasing, while in Scotland the species increased by 29% and in Wales by 63%.
Better news for kingfishers
Another worrying trend is the decline since 1970 of 83% in the spotted flycatcher, once relatively common in woodland and large gardens.
The organisers say the increase in numbers of blackbirds and song thrushes represents apparent reversals of long-term trends, and may be linked to climate patterns.
A familiar springtime visitor to much of the UK, the cuckoo, showed a 25% decline since 1994.
The organisers have now made the survey partly web-based: BBS Online will allow volunteers to enter bird (and mammal and habitat) data collected from their squares into a new survey database.
They are keen to hear from anyone who would like to volunteer to take part in future surveys.