Ravens are again being seen in the skies over north Oxfordshire as the big black birds make a recovery, spreading eastwards from their strongholds in Wales and the West Country.

At one time, ravens were fairly common though perhaps not quite so numerous as crows or rooks. Until recently, they had virtually disappeared from central England.

In the past five to six years, members of Banbury Ornithological Society (BOS) have noticed they are back in Oxfordshire.

Trevor Easterbrook, bird recorder for BOS, attributed their return to the availability of rabbits, which have generally recovered from the myxomatosis outbreaks that devastated their numbers.

Rabbits are also more numerous because there are fewer working gamekeepers to trap or shoot them.

“Ravens mainly live off carrion — dead rabbits and other small mammals. Although ravens are not seen all that frequently in the area, we have records of several breeding pairs. Often when we go out we hear their deep ark-ark cry, so we know they are there and moving about,” said Trevor.

Ravens like to nest in pine woodland and in pines in large gardens.

“They also nest in pylons and in towers,” added Trevor.

Ravens have also been joined in the sky by buzzards which are making a gradual migration from west to east and are now almost regarded as a common sight.

Rabbits are food for buzzards too.

Another bird that is being logged more and more in the region is the cormorant, usually found on the coast where there is a plentiful supply of fish.

“We think the cormorants have been making their way inland up rivers like the Thames and Cherwell, perhaps due to a decline in fish at the coast.

“One reason for cormorants being attracted to this region is that there are many more lakes and ponds than before.

“Some farmers have been diversifying from traditional agriculture by creating lakes for anglers and so providing food for cormorants,” added Trevor.

The return of ravens, buzzards and the arrival of cormorants are just three of the changes in the bird population that have been recorded by members of BOS in the past 50 or so years.

The society was formed by a small group of enthusiastic birdwatchers in 1953, after attending a series of evening classes in Banbury run by the late Bruce Campbell, the celebrated Oxfordshire naturalist. Mr Campbell became their first president.

Early on, members decided they would be more than just “twitchers” — people who race to any part of the country when a rare bird is spotted stopping over.

They wanted to record all the different species to be found in an area within a few miles radius of Banbury.

However, before long they stretched their wings and began working in much of the area that is now covered by Cherwell District Council, while also spilling over into the neighbouring parts of Warwickshire and Northamptonshire.

They divided the area into 10km square grids, with Banbury roughly in the middle and going as far west as Chipping Norton, to Byfield and Avon Dassett in the north and to Bicester in the south-east.

Members chose which grids or squares they would research.

A few years later, they discovered they were pioneers in this kind of grid coverage as it was adopted nationally by the British Trust for Ornithology.

“It was then decided we would make an annual breeding bird survey of 25 different species of birds.

“We are now about three-quarters of our way through our second 25-year rota of taking one species a year,” said Trevor.

In the early days, members recorded their findings on cards and posted or handed them in to Trevor.

The arrival of laptop computers has simplified and speeded up the process, although some members still stick to the cards.

Not only are birds recorded, but also the types of habitats in which they are found.

“We make something like 10,000 records in a year.

“The information on habitats is important so we know what is out there,” said Trevor.

More recently, members have been making more general surveys on habitats and have been surprised what they have found. “For instance they have discovered the new lakes that often cannot be seen from ground level but only from hillsides overlooking a site,” said Trevor.

Their findings are regularly reported to the British Trust for Ornithology and the Royal Society for the Protection of Birds.

“Over the year we have found that our results on bird populations declining or increasing are mirrored by the national surveys,” said Trevor.

However, there are some variations locally, with some species bucking the national trends.

For example, Trevor cited the survival of corn buntings in this region.

“Corn buntings are not numerous, but they seem to be doing better round here than in other parts of the country,” he said.

Birds that have fluctuated in the area are the marsh tit and the willow tit, while skylarks have made a bit of a recovery. Although starlings have declined they are not expected to disappear altogether.

Grey partridges are becoming rare due to changes in farming practices where winter-sown cereal crops can mean that fields are not left to stubble so long after harvesting.

Nuthatches have remained fairly constant in the area and goldfinches have done reasonably well.

One factor behind the variations in bird populations is the nature of a region, says Trevor.

Dairy farming is found a lot in the west while the east is predominantly a cereal-crop growing area.

In central England we have more of a mix of the two types of farming.