Winter song of the warmer days to come

After an all-too-brief respite, snow and ice are back, making life difficult again for many birds.

But it is still possible to hear the exuberant song of the Cetti's warbler, a reminder of warmer days to come.

One has been heard again at the Yorkshire Wildlife Trust's Potteric Carr reserve near Doncaster, and this normally skulking bird was in view for some ten minutes, foraging among the reeds.

This is the thirdwinter running that this warbler, resident in Britain throughout the year, has been present at Potteric, while at the end of last month three were present in the reedbed at the RSPB's Old Moor reserve near Barnsley.

How a bird originating in the Mediterranean has managed to expand northwards and consolidate its place among Britain's birds is a remarkable story. At the beginning of the 20th centurythe Cetti's warbler, named after an Italian scientist and naturalist, was confined to the Mediterranean but then it began to expand through France and the first pair bred in southern England in 1973.

Despite the occasional setback, such as the winter of 1986-87 when there was a population crash, they have continued to colonise sites in the south-east, midlands and Wales. The first pair bred in Yorkshire at the Tophill Low reserve in 2006.

Their future in this country would seem to be secure but the rate of population increase has slowed due to more severe winters. It could be that the present population of between 700 and 1,000 pairs is approaching maximum size and Yorkshire could prove its northernmost limit.

Another bird more associated with summer, the blackcap, is being seen in more winter gardens again and sightings are likely to reach a peak in the New Year.

These are birds migrating from central Europe for the winter instead of heading south to Africa.

There are many reports of blackcaps being extremely aggressive, chasing away other birds up to the size of blackbirds and wood pigeons with only robins standing their ground.

Many reserves have been iced over, with birds concentrated at the few remaining areas of open water. Some 30,000 wildfowl have been on the ice-free River Derwent at English Nature's Lower Derwent Valley reserve between York and Selby, among them up to 76 whooper swans, while eight Bewick's swans have also roosted there.

Signs have gone up in the valley along with other nature reserves asking visitors to modify their routes to avoid disturbing birds struggling in the harsh weather.

Woodcocks have continued to arrive all along the east coast with a record count for Filey of 161 on Friday last week while snipe and curlewshave been seen feeding on anyavailable ice-free patch of ground.

Little egrets were reported at Clapham in the Yorkshire Dales and on the River Don at Meadowhall, Sheffield.

A great grey shrike is presentalong the road onthe east sideof the River Wharfe opposite Bolton Priory.

A long-eared owl is still being seen at the Fairburn Ings reserve near Castleford – directions from the visitor centre –while three pink-footed geese and five mealy redpolls are among other sightings.

Bitterns have been seen out on the ice in a number of places, including Potteric Carr and the RSPB is suggesting that reserves with overwintering bitterns present should again begin supplementary feeding.

A bittern event is being held at the reserve on Saturday January 29 costing 20pp which includes lunch, a lecture and guided walks. Ring 01 302 570077.

CW 18/12/10