Review – October Indoor Meeting – David White (BTO) – Breeding Bird Survey Review

David White gave us a highly-informative yet lively talk on the work of the BTO.  He outlined the range of its surveys and the uses of the data derived from them, and focused on the Breeding Bird Survey (BBS), showing data from 1995-present for a range of species.

Like other members (I suspect) I had heard of the BBS without really knowing exactly what the volunteers (currently over 2700) actually do.  David described the procedure clearly, together with the related approach used for the Wetland Breeding Bird Survey.  Cambridgeshire is relatively well-represented among the more than 3900 1km squares currently covered, such that it was possible for David to present data for some species at county level, while other species were considered regionally or nationally.

What emerges from the data sometimes struck a chord with what we may have noticed on our own patch – the ubiquitous Woodpigeon, the increased numbers of Goldfinches from about 2010, or the catastrophic fall in Turtle Dove numbers.  Explanations for some changes are not hard to identify – an increase in Buzzards since the banning of the pesticide DDT, or the decrease in Greenfinches after 2005 due to the disease trichomonosis.  However, other aspects are not easily explained, including geographical differences – for example, House Martins and Spotted Flycatchers show moderate declines in England but have increased in Scotland and Ireland.  Although there is not sufficient data about recently-established species such as Common Crane for serial analysis, data from the BBS will contribute to the next edition of the Bird Atlas.

David is Engagement and Surveys Officer (England) for the BTO; appropriately, this was easily one of the best data-driven talks that has been given to our Group, provoking much interesting discussion. For more information on the survey follow the BTO link.

Tony Corps