The British Trust for Ornithology is updating two of the most important bird atlases covering the UK and is appealing for volunteer assistance, writes ELIZABETH EDWARDS

Volunteers are needed to update one of the major reference works for birdwatchers. The British Trust for Ornithology's Breeding Bird Atlas and Wintering Bird Atlas. are 15 and 20-years-old respectively and the BTO is to begin from November 1 a four-year programme of fieldwork to update both.

More than 250 species in Britain and Ireland will be surveyed, including 40 species that are red-listed and 121 amber-listed and of conservation concern.

To carry out this work, it needs observers throughout the country and it is hoping that its 30,000 members will be joined by many volunteers.

"We need to motivate as many birdwatchers as possible to take part in this nationally-important survey," said Dawn Balmer, the atlas co-ordinator.

In Oxfordshire, both Oxford and Banbury ornithological societies will be taking part and will welcome more observers. In other areas of Oxfordshire and in neighbouring counties, the regional organisers will also welcome assistance.

The survey is carried out in two ways.

There are timed visits of one or two hours twice during the winter and the breeding season to record species, give an estimate of their number and note whether there are signs of breeding, such as nest-building or food for young.

The other is roving records of information from an identified area of 10km square, in both breeding and winter seasons and in a range of habitats. As well as providing these roving reports from their home area, people visiting a different part of the country can submit data from there as well.

If these are from an area where there are few resident birdwatchers, they can make a vital contribution in filling in important gaps in the completion of the maps.

"This 'stock-take' of our birds will reveal fascinating changes in the status of species since the last Breeding Atlas 1988-1991 and Wintering Atlas 1981-84," said Dawn.

"The atlas will tell us if farmland bird populations have responded to the implementation of agri-environment schemes since the early 1990s and how our woodland birds are faring.

"Where will we still be able to find willow tits and wood warblers?

"We know that we will find more Little Egrets (see below) and buzzards but the real excitement will be in discovering less obvious success stories. Hopefully, these might balance out the expected bad news for species such as the cuckoo and snipe.

"The findings of Bird Atlas 2007-11 will shape the direction of conservation action over the coming decades. It is a tremendous opportunity for us all to do our bit."

A bird that it is expected that it may be difficult to find is the Lesser spotted woodpecker, whose declining population is attributed to the loss of the elm trees in which it prefers to nest and to the fragmentation of woodland and the loss of mature broad-leaved trees.

The green woodpecker may be more evident, possibly as a result of the recent mild winters which have led to its population moving northwards through Britain.

Conversely, the milder winter, also experienced on the continent, may be resulting in lapwings having less need to come to Britain for the winter. This may also be the reason for fewer teal to retreat here from Scandinavia and Russia as they normally do in late November.

Other issues of interest will be whether local barn-owl populations have been helped by conservation measures, whether stewardship schemes are beginning to prove of value for farmland species such as the yellow-hammer and whether supplies such as sunflower hearts and nyger seed provided in bird-feeders in gardens are reversing the decline in goldfinches.

The combination of the breeding and wintering atlas surveys will help in understanding how goldfinches move about to find food between summer and winter.

The cost of the survey is immense and the BTO is inviting businesses to raise both their own profile and that of a species by, for example, a courier service sponsoring the swift or a vegetable producer the fieldfare.

Anybody who would like to be involved can contact the society on 01608 644425 or at the banburyornithologicalsociety.org.uk website. Details of regional organisers are available at www.birdatlas.net, or from the BTO on 01842 750050.