Britain's bird of the year in 2008 may turn out to be a beautiful white heron whose original home was Africa. The cattle egret, which has been spreading steadily northwards through Europe, perhaps because of climate change, is thought to be on the point of colonising southern England.

This winter, so many of the birds are present along coasts in the south and west that breeding is thought likely to happen soon, not least because the process appears to be a replica of colonisation by a closely related species, the little egret, in the mid-1990s.

From being a rare vagrant which delighted birdwatchers, little egrets began to arrive in substantial numbers on the south coast, and in 1996 a pair bred for the first time in Britain in the heronry on Brownsea Island in Poole harbour, Dorset. Their population has doubled every year since and Britain now has several hundred breeding pairs. Birdwatchers and ornithologists alike think the cattle egret may be about to do the same.

Cornwall has been the main centre of sightings this winter, with as many as 18 birds seen together at Drift reservoir near Penzance, and up to 15 more at another 20 locations, including sites in Devon and Dorset.

"The recent arrivals of large numbers of cattle egrets into southern Britain has renewed optimism that this bird may nest successfully this year, somewhere in England, for the first time," said Graham Madge, a spokesman for the RSPB.

"Cattle egrets are one of a number of species thought likely to nest here in future as our climate becomes milder," said Mark Grantham of the British Trust for Ornithology. "So many have arrived recently the prospect has become stronger but, because they nest communally, it will probably only happen if sufficient gather in a location suitable for a colony."

Cattle egrets, smaller than little egrets and further distinguished by a pale orange crown and breast in the breeding season, are so-called because they regularly feed beside cows, catching frogs and insects the cattle disturb.

They are not the only new arrivals Britain may see as first-time breeding species in 2008. Purple herons, which are smaller and more colourful relatives of our familiar grey heron, attempted to nest last summer at the RSPB's reserve at Minsmere on the Suffolk coast, but their nest was washed away in the torrential rainstorms of June. A renewed attempt this year would be no surprise. Spoonbills, pure white, egret-sized wading birds whose bills have a spatula-like tip, are also thought to be on the point of nesting in Britain.

The serin, a close relative of the canary, may also be on its way.

Flocking to Britain: The birds colonising these islands as the climate warms

* Cattle egret (Bubulcus ibis)
A small white heron with a compact yellow bill. Nests in colonies in trees by lakes and rivers, but feeds in dry grassland, often near cows.

* Little egret (Egretta garzetta)
Slightly larger predecessor of the cattle egret, colonising Britain 12 years ago. Slim and elegant, with black legs and long black bill. Also nests in colonies, sometimes with grey herons.

* Purple heron Ardea purpurea )
An attractive heron common in pats of Europe but which has not hitherto bred in Britain. A nesting attempt last summer came to nothing when the nest was washed away in torrential rainstorms.

* Spoonbill (Platalea leucorodia)
A wading bird which is quite unmistakeable because of its curious bill, the tip of which is flattened like a spoon. Several nesting attempts have been made already in Britain and it is possible that it has already nested without the fact being widely realised.

* Serin (Serinus serinus)
A greenish-yellow finch, quite closely related to the canary, which has bred in Britain several times in the past 40 years, but never continuously.

(By Michael McCarthy, The Independent, 07/01/2008)