Worcestershire Record No. 26 April 2009 pp. 22-23

Harry Green

Built on extensive national fieldwork by many people the BTO has produced three major atlases of bird distribution using the 10X10km squares of the national grids of Great Britain and Ireland. The years of the fieldwork for these atlas are as follows:

Breeding 1968-1972

Winter 1981-1984

Breeding 1988-1991

Fieldwork is now in progress for the production of a new atlas of both breeding and wintering birds to be based on findings during the years 2007-2011. Like the 1988-91 breeding birds atlas and the 1981-84 winter birds atlas the new atlas will show both distribution and estimated population sizes for each species. Casual observation over the last18 years suggest that the new atlas will show some dramatic changes, both increases and declines. For example some farmland birds such as Linnet, Yellowhammer and Corn bunting are likely to show great declines. Buzzards, Ravens, and Nuthatches will show considerable expansion. Little Egrets now breeds in many places and did not even appear in the last atlas!

To make this possible records are being collected in two main ways:

All records to build up comprehensive lists of each species found winter and summer in every 10x10km square.

Timed tetrad counts (TTVs) of 1 or 2 hours to enable population estimates to be made.

During the breeding season indications of breeding (possible, probable, confirmed) are also collected.

This project is the most ambitious yet and will reveal many changes. A major innovation is that many records can be entered directly by the recorder on to the Bird Atlas website so speeding up the computerising of records for analysis. Paper based records as of course still very welcome using the BTO forms.

To illustrate some of the changes shown by the previous atlases here follow a few examples. The changes during the breeding season are those revealed by the second breeding atlas compared with the first.

The Collared Dove which arrived in Britain around 1950 was shown by the 1988-91 Atlas to have continued to colonise Ireland and northern Britain. Nowadays this species is so common that many people think it has always been with us. The invasion followed a NW explosive expansion across Europe from Asia Minor and is probably based on genetic change within the species.

The Nuthatch continued to extend its range northwards and eastwards. This change may have continued since 1990 and is probably based on milder winters leading to better survival rates.

The Blackcap showed great changes both in Breeding and Wintering distributions. In the summer records were made in new 10x10km squares in Scotland and Ireland although other squares had apparently been vacated. The greatest changes occurred in winter. In the 1950s and before wintering blackcaps were extremely rare in Britain. By 1990 they were commonly seen in winter in many parts of the British Isles especially in SE England and the Severn Valley. This change probably follows better survival due to mild winters amongst birds which migrated NW rather than SW from central Europe in autumn. Many of the winter birds seem to flourish in gardens rather than the wider countryside. It is thought that these wintering birds generally return to Europe to breed. The changes in summer distribution is less clear and the new atlas may be instructive.

The Buzzard was driven back to Wales and parts of western England and Scotland by the 1950s due to persecution and they were scarce birds in Worcestershire at that time. By 1990 they had re-colonised the county, especially in the west, and were moving steadily eastwards. This expansion of range has continued. Ravens have shown a similar change but this was not apparent by 1990 although since then most of Worcestershire has been invaded and the species is also moving steadily eastwards.

Most of the 10x10 km squares occupied by Cetti’s Warbler by 1990 were new records. This over-wintering wetland warbler has continued to increase probably because of better survival in mild winters.

The Little Egret was only mentioned in the 1988-91 Atlas in the last appendix! They had only been recorded in three 10x10km squares in the whole of Britain and Ireland during the breeding season. They are now seen in many places and breed in England. They may well first breed in Worcestershire during the new atlas survey years 2007-2011.

What changes will 2007-2011 show? There have been many changes in recent years – mostly declines – based on the results of other surveys. The new atlas will be an important record. Please help collect data! Worcestershire is becoming well-covered both summer and winter but there are many ‘holes’. Please help fill them. The Atlas website will reveal what is uncovered www.birdatlas.net otherwise give me a ring on 01386 710377. As well as general recording and TTVs hard evidence of breeding is always welcome and I would be glad to receive records. Date, place, the evidence, grid reference if possible, and your details – and the species!