The RSPB is worried by the continuing decline in numbers of woodland birds in Oxfordshire, reflecting dramatic falls across the UK, writes PETER BARRINGTON

Woodland birds in Oxfordshire are in decline, reflecting a similar fall in numbers among other countryside species and in garden birds over recent decades.

The reasons for the drop may be difficult to define but a lack of ground cover and mild winters are known to be contributory factors.

Colin Wilkinson, a conservation officer based at the Banbury regional office of the Royal Society for the Protection of Birds, gave an example of the problems from his own observations.

"Naturally, I do a lot of birdwatching, often in woods around Hook Norton, and I have not seen any Spotted flycatchers for three years," he said.

Colin's findings match up with those of RSPB and the British Trust for Ornithology surveys that have recorded a loss of numbers in eight out of 33 species.

Among the birds on the list in decline are the Spotted flycatcher, Lesser spotted woodpeckers, Willow warblers, Willow tit and Tree pipit.

Surveys between the two conservation groups do show some variations. For example, the BTO results show there has been a drop of 43 per cent in the case of the Lesser spotted woodpeckers, while the RSPB puts the figure at minus 59 per cent.

Similarly, the Spotted flycatcher shows a huge fall of 70 per cent in the BTO survey, but only records a fall of 36 per cent with the RSPB.

But while figures cannot be precise, they do indicate that several species fall into the category of "cause for concern".

Other birds that have shown a worrying decline are Pied flycatcher, hawfinch and redstart.

Colin said: "With our woodlands bird survey we are about at the same point now as we were 20 years ago with our surveys of countryside and garden birds. We are at a very early stage of our observations but there are some reasons that we believe are attributable to the diminishing numbers."

One of these is the lack of ground cover to be found in woodlands - the bramble bushes, herbs and other vegetation that reaches up to knee height and sometimes higher.

"I think that in some Oxfordshire woodlands these days there is very little ground cover that is essential for birdlife. For example, there is not a lot of hazel coppicing going on as there was in the past so that can reduce the amount of ground cover."

Woodland management is important to ensure there is not a decline in standing trees. In some woodlands the trees are old and this can lead to thick canopies that prevent the light from getting through to ground vegetation.

A second factor is the prevalence of deer, particularly roe and muntjac, which graze heavily on woodland vegetation. Deer grazing puts pressure on ground cover plants like bramble and herbs and this led to an increase in bracken growth, which is unsuitable for birds.

The small muntjac, which originates from South-East Asia, has been particularly successful in Oxfordshire and the Chilterns ever since some escaped decades ago from an estate in Buckinghamshire.

Other factors include the drying out of wetlands and ponds in woods.

Colin pointed out that some birds, like woodpeckers, need a supply of dead trees and tree limbs to create nests. However, some woods are very well managed, such as the Oxford University-run Wytham Woods, a Site of Special Scientific Interest.

The need for landowners to consider woodland management is important, according to Julia Gallagher, a fellow RSPB conservation officer at Banbury.

"We need to get the message across to landowners of the importance that small woods have for the bird population," she said.

Landowners should appreciate that even scrubland, which sometimes develops into new woods, can help birds. Ash, hawthorn and blackthorn are often found in scrublands.

The long series of mild winters is also seen as a factor in the size of bird populations.

While migration flight patterns take a long time to change it was already known that medium-distance migrants like the chiff chaff, blackcaps and some warblers were not now flying further south to winter than Cornwall.

Colin pointed out: "These birds used to fly to southern Europe but warmer winters here mean they do not have to migrate so far away."

This can lead to competition among year-round resident birds and migrants for food.

Even the gradual expansion of the Sahara Desert has also prevented other migrants from flying even further south. They might go no further than southern Spain and France.

But the picture is not completely bleak. Some species, such as Greater spotted and Green woodpeckers, Coal tits and Blue tits have increased.