The cuckoo and yellowhammer are among the species suffering the sharpest declines in the British Trust for Ornithology's latest survey, writes ELIZABETH EDWARDS

I am evidently not alone in having missed the sights of the yellowhammer and the sounds of the cuckoo in recent summers, for the British Trust for Ornithology's Breeding Bird Survey show that these species are becoming increasingly rare.

In the south-east, including Oxfordshire, the yellowhammer, which is red-listed as a UK Biodiversity Action Plan priority species, has declined by 38 per cent since 1993 and the yellow-listed cuckoo shows a drop of 55 per cent.

These are two of 40 species whose declines are considered significant. The cuckoo, however, is not the only species whose decline has been notable across all regions.

The Breeding Bird Survey is carried out by volunteers who during the breeding season between April and June visit a random one metre square to count all the birds they observe. Throughout the country, they visited 3,604 squares and recorded 220 species.

In 2006 Oxfordshire had the honour of having the most species-rich square, with 71 species recorded by a volunteer who visited a location that included farmland, woodland and waterside habitats near the Wiltshire border.

From the 2007 results, 27 species were found to have declined significantly and 46 increased.

The negative findings included those for the willow tit, wood warbler, turtle dove, spotted flycatcher, all of which declined by more than half, and the yellow wagtail, swift, grey partridge, curlew, kestrel, linnet, little owl and starling.

Those on the positive side included the great spotted woodpecker, the raven, tufted duck, buzzard, red kite, great tit, goldcrest, grasshopper warbler, the greylag goose and Canada goose - all increased by more than half.

Among priority species there was good news. The red-listed song thrush has shown an increase in some regions, as have the grasshopper warbler and the reed bunting and the yellow-listed dunnock or hedge sparrow.

The south-east is one of the regions where the yellow-listed green woodpecker is more present. The house sparrow and bullfinch, both yellow-listed, declined.

The wood pigeon was the species seen in the greatest number, followed by the chaffinch and the blackbird. Overall more than one million birds were recorded.

Throughout the UK, three species - the great spotted woodpecker, Canada goose and raven - showed increases of more than 100 per cent, the stonechat and greylag goose doubled in numbers and the sparrowhawk trebled.

But the largest percentage rise was - surprisingly - for the ring-necked parakeet, the species originally imported from India as a cage bird, has spread widely.

BBS national organiser Kate Risely found that the findings relating to woodland birds are the cause for most concern. The greatest losses are those of the willow tit, by 77 per cent.

Kate said: "This is not due to habitat as, overall, we probably have more woodland than ever, but the tree composition and age structure of our woods have changed."

But she welcomes the good news about the species with expanding populations.

"Many of the species showing the biggest increases are also expanding across the UK, notably the stonechat, the nuthatch and the buzzard.

"Buzzards are spreading from their western strongholds, thanks to reduced persecution and the recovering of rabbit populations from the effects of myxomatosis."

Stonechats are also spreading back eastwards from the temperate western coastal areas, and nuthatches are moving northwards.

"Is this an indication of climate change?" wonders Kate.

Farmland birds saw the same significant trend. Declines were recorded in the grey partridge, kestrel, lapwing, turtle dove, skylark, yellow wagtail, starling, linnet, yellowhammer and corn bunting.

In the face of these losses, the benefits of domestic gardens are all the more valuable.

Birds that tend to make to use of gardens, such as the dunnock, robin, blackbird, song thrush, coal tit, blue tit, great tit, chaffinch, green finch and goldfinch, have all shown increases.

"Most birds occur in more than one habitat," said Nancy Ockendon, of the BTO, and their success may vary between habitats.

The survey results provide essential data for national conservation policies and are used in the planning of Environmental Stewardship Schemes and will be used to investigate the effect of the Countryside and Rights of Way Act and of Special Protection Areas on bird populations.