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.

Changing waterfowl require greater understanding

The latest review of waterbird populations in the UK makes interesting reading. At first glance it suggests contrasting fortunes for many of the species with which we share these islands. The review, jointly published by the BTO, RSPB and JNCC, stems from the efforts of some 3,000 volunteer counters. These volunteers participate in the synchronised monthly counts that take place across our many inland and coastal waterbodies.

While some species reached new ‘highs’ in terms of their population levels, others reached all-time lows. An examination of the ‘winners’ and ‘losers’ reveals that many of the ‘winners’ are introduced species whose naturalised populations continue to expand. These include Egyptian Goose, Mandarin Duck and Barnacle Goose. However, in with these are genuine colonists like Little Egret, a species expanding north on the back of global climate change.

The numbers of some species reflect breeding conditions elsewhere, the UK being a wintering ground with little or no breeding population of its own. A poor breeding season elsewhere may see fewer birds available to make the journey to our shores. The recent downtown in wintering numbers of Bewick’s Swans was once thought to be linked to a contraction eastwards in the wider European wintering range. However, recent research has revealed a decline in the overall population rather than just a shift in distribution. In contrast, our population of wintering Whooper Swans has continued to increase, with most of our visiting Whoopers arriving from Icelandic breeding grounds. The nature of the survey also enables the volunteer counters to gather information on breeding success for some species. In the case of the Whooper Swan, cygnets accounted for 16.8% of the birds present, slightly up on the previous winter.

The estuaries around Britain & Ireland are important wintering sites for many wading birds and these are also surveyed by the volunteers. Again fortunes appear mixed, with some notable increases seen in Avocet (a real conservation success story), Grey Plover and Sanderling. Balanced against this is the apparent news that Ringed Plover and Dunlin have both hit all time lows. Britain has eight sites of international importance for Ringed Plover but, while the decline might seem worrying, news of increasing numbers at sites elsewhere in Europe (notably The Netherlands) suggests that what we are actually seeing is an eastward shift in the core wintering range, perhaps linked to a run of mild winters.

Taken as a whole, this report highlights the need to monitor the changing fortunes of these birds at a much wider spatial scale, since a decline here may not mean that the population is falling, merely that it is now wintering elsewhere. Fortunately, our knowledge of waterbirds is increasing, placing our understanding into a wider context.