Press Releases - July/Aug 2005 - Item 8

No. 2005/08/25A
26 August 2005

Surrey residents invade Berkshire

Surrey residents are invading Berkshire! These two birds look different enough to be separate species, however, both are in fact the familiar Great Tit. The latest issue of the BTO’s Garden BirdWatch magazine, Bird Table, features an article on the occurrence of ‘black-headed’ Great Tits in Surrey and their recent colonisation of Berkshire. The BTO needs garden owners to help record these and other birds in private gardens around the county.

The bird on the left is a typical, everyday, run-of-the-mill Great Tit, but the bird on the right has a completely black head, due to a genetic mutation causing melanism (the laying down of extra pigment in the feathers). In Surrey, regular sightings of these ‘black-headed’ Great Tits can be traced back to the 1940s within a core area between Esher, Epsom and Leatherhead. However, this population seems to have shifted westwards in recent years to an area to the northwest of Woking and the first reports are now coming in from Berkshire. It would be interesting to know their current distribution within Berkshire and the BTO needs your help in mapping their occurrence in gardens.

Melanism can occur for a variety of reasons. However, for these Great Tits there appears to be a genetic component to this change in appearance, as family groups have been seen where both parents and offspring have the all black head. Birds sometimes show variation in the colour of their plumage that may be different to that normally seen, with albino individuals being the most striking example.

The BTO/CJ Garden BirdWatch scheme needs people in Berkshire to record the occurrence of the ‘black-headed’ Great Tits and other birds in their gardens. It has been running since 1995 and has highlighted changes in the use of our gardens by different bird species. Some 306 participants currently take part in Garden BirdWatch in Berkshire and send in simple weekly records of the bird species using their gardens. To receive a free information pack, phone 01842 750050 or write to GBW, Room 26, British Trust for Ornithology, The Nunnery, Thetford, Norfolk IP24 2PU.

Notes for Editors

1) The BTO/CJ Garden BirdWatch. The BTO/CJ Garden BirdWatch is the only nationwide survey of garden birds to run weekly throughout the year, providing important information on how birds use gardens, and how this use changes over time. Currently, some 16,500 people take part in the project with 306 in Berkshire. The BTO/CJ Garden BirdWatch is funded by participants’ contributions and supported by CJ WildBird Foods Ltd and is the largest year round survey of garden birds anywhere in the world. For more information see www.bto.org/gbw

2) Bird Table Magazine. Bird Table magazine is published quarterly and sent free to all BTO/CJ Garden BirdWatchers. An annual subscription to the project costs just £12 and all new joiners will receive a free copy of the BTO/CJ Garden BirdWatch Book (which normally retails for £9.99). An electronic version of the Bird Table article on ‘Black-headed’ Great Tits is available for Editors and can be requested from

3) Great Tit Facts. There are over 2 million pairs of Great Tits in the UK. The female lays between 6 and 11 eggs; these are incubated for up to 15 days and the young will have fledged after a further 16-22 days. In the spring and summer Great Tits tend to feed mainly on invertebrates taken from leaves, but in autumn the diet slowly changes, incorporating more seeds and fruits. Great Tits are found in 80% of Berkshire’s gardens.

4) Colour photographs. The images shown overleaf, together with other garden bird images, are freely available for use in association with this press release. Please contact to request an electronic version.

5) CJ WildBird Foods. CJ WildBird Foods is Europe’s leading supplier of bird food and bird feeding products. CJ WildBird Foods has been responsible for a number of significant developments within the bird food and feeding industry, including the introduction of black sunflower seeds to the UK as a major new bird food and the development of specialist seed mixes for use in tubular feeders. The company has also been supporting research into the changing fortunes of garden bird populations, most notably through the BTO/CJ Garden BirdWatch.

For further information please contact:

Mike Toms on 01842 750050 or e-mail: (during office hours)
Martin Fowlie on 01842 750050, e-mail: (during office hours)

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