Why on earth is the BTO organising a Winter Thrushes Survey when we have just finished Bird Atlas fieldwork? It’s a simple question with a simple answer that was provided by David Snow in 1987. Writing in the species account for Redwing in The Atlas of Wintering Birds in Britain and Ireland, edited by Peter Lack and based on records collected between 1981 and 1984, he said:

“Any attempt to estimate the size of the wintering population of Redwings in Britain and Ireland meets with the same problem as for the Fieldfare: the numbers vary from year to year, and also in the course of a single winter, and major shifts of population may take place in response to weather and feeding conditions. Synchronous counts over a large number of sample areas would enable a rough estimate to be made, but this would be a major piece of collaborative fieldwork.”

Twenty-five years later we’re asking volunteers to undertake repeat walks to favourite spots through the course of two winters, with a particular focus on a set of coordinated counts over the Christmas and New Year period.

In his species account, David Snow estimated that these islands provide a winter home for possibly one million birds but many people feel that this number may have fallen over the years. Potentially, we could recalculate the number, based on the broad assumptions made for the last atlas, and it would not be surprising if the process produced a smaller figure. There certainly seems to be less talk of the large roosts that were a feature of chat at bird clubs in the 1970s and early 1980s.

  Migration map: Time to Fly by Jim Flegg

 September and October will see the major arrivals of Redwings into the UK, as birds cross the North Sea, from Scandinavia and Russia, and Icelandic birds arrive in western areas, as shown in the map from Time to Fly by Jim Flegg. There are some unsurprising geographical links, with more-strikingly-marked Icelandic birds, of the race coburni, being rarely seen in East Anglia.

By the time that autumn turns to winter, Redwings will have largely finished their journeys, settling in the warmer and relatively frost-free areas away from the east coast. Hard weather may force them to migrate further, with Scandinavian/Russian birds (the iliacus race) continuing westwards to Ireland or southwards into southern Europe. To some degree, iliacus Redwings can be somewhat nomadic, with individuals taking different routes in different years, when leaving their breeding areas. The blue dots indicate birds found in subsequent winters, wearing BTO rings. The bird in a Herefordshire orchard this winter may have been in Portugal, Greece, or even Iran last winter.

Redwing winter abundance map for Bird Atlas 2007-11

In fieldwork for Bird Atlas 2007-11, Redwings were recorded in over 90% of 10-km squares but, as can be seen in the map alongside which models the abundance of birds using count data from thousands of volunteers, their distribution is far from even. Key counties in the southwest, the Welsh borders and the Midlands support high numbers of birds and are probably very important to the conservation of the species.

Redwings are red-listed in the UK because we have a very small breeding population, restricted in range to the northern third of Scotland.   In 1968-72, Redwings were confirmed breeding in 54 10-km squares (57 possible/probable). In 1988-91, comparable figures were 46 (90) but this time around numbers were down to 18 (58), although these figures are still to be finally confirmed.

Although recognising that we should be concerned about the small number of breeding Redwings, our larger responsibility must surely be for the hundreds of thousands of Redwings that rely on our hedgerows, fields and orchards between October and March. The Winter Thrushes Survey should help us to start to understand just what it is that winter thrushes are looking for when they seek out these islands as a winter refuge, especially the relative importance of hedgerows, fields, orchards and gardens. Records from any of these habitats will be very much appreciated.

By Graham Appleton

More BirdFacts for this species Winter Thrushes Survey

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