Thursday, 6 January 2011

Grey geese harbour a vagrant

With the exception of the chunky Greylag Goose, our wintering grey geese can prove something of an identification challenge, especially when seen at a distance or in the dull light of a winter’s afternoon. While the Pink-footed Geese, whose skeins sometimes number hundreds of individuals, are perhaps the best known of these winter visitors, there are others that provide the real draw for many of the county’s birdwatchers.

White-fronted Geese arrive from distant breeding grounds that stretch across the Russian and Siberian tundra, with most wintering in North Norfolk, around the Broads or down into Suffolk. The numbers wintering in our region are small when compared to those wintering in the south-west of England, notably at Slimbridge, and much reduced compared to the peak numbers seen here during the 1940s. At that time, up to 4,000 of these birds could be found feeding on the marshes at Halvergate or roosting on sands at Scroby. Today, numbers are a more modest 500-600. White-fronted Geese also breed in Greenland and it is birds from this breeding population that winter in Scotland and Ireland. Only occasional individuals from the Greenland population reach East Anglia, most often appearing in the company of the large flocks of pink-foots that feed on the fields inland from the North Norfolk coast.

The Yare valley is home to visiting Bean Geese, a species rather similar in appearance to the more familiar Pink-footed Goose. Here, the marshes at Cantley and Buckenham have become reliable sites at which to see these birds, with 100-150 present most winters. Cantley seems to be the more favoured of the two marshes, with birds only spending more time at Buckenham if disturbance levels at Cantley increase.

Over the last few weeks there has been a rare Lesser White-fronted Goose in with the other geese at Cantley. This species breeds in the narrow boreal zone, dominated by birch and willow scrub, which stretches across northern Fennoscandia and Russia. The westernmost parts of this population have declined dramatically, reducing the chances of individuals reaching our shores for the winter. The eastern component of the breeding population winters on the coastal plains of the Black and Caspian Seas, east to China, and so is far less likely to reach us. The situation has been confused, however, by recent attempts to reintroduce the species into former Fennoscandian haunts. The reintroduction programme, which involves the colour ringing of young birds raised by foster parent Barnacle Geese, has seen an increase in the numbers of Lesser White-fronted Geese wintering in the Netherlands and it is quite possible that one of the consequences of this work is the occurrence of reintroduced birds (or their young) turning up here in the winter.

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