Thames and Chiltern Bird Atlas

The atlas covers five contiguous counties: Oxfordshire, Berkshire, Buckinghamshire, Hertfordshire and Bedfordshire, of central southern England. These inland counties all undertook fieldwork for Bird Atlas 2007 - 11 in both winter (November - February) and breeding (April - July) seasons. Four winters, from November 2007, and four breeding seasons, from 2008, were surveyed. In Oxfordshire limited survey activity was undertaken for a further winter and breeding season to fill a few gaps in coverage.

Breeding evidence was classified as either Possible (presence in suitable habitat), Probable (typically display or singing males) or Confirmed (typically an active nest, parents carrying food or recently fledged young). Distributions are shown at the tetrad (2x2 km) scale in contrast to the national 10km square atlas. Many widespread species which are declining can still be confirmed as breeding in most 10km squares, but the declines becomes clear at the tetrad scale. Examples include Willow Warbler and Spotted Flycatcher which both appear ubiquitous across our region at the 10km scale of the national atlas. In 2007 - 12, in addition to casual visits, almost all Oxfordshire tetrads were visited twice in one breeding season and twice in one winter to count all birds in one or two-hour timed tetrad visits (TTVs). A comparison of these counts with the mean values is used to show the variation in species abundance across the region.

The results for the breeding season can be compared with county surveys approximately 20 years prior to 2007 - 11, and for Hertfordshire and Bedfordshire a third survey 40 years before. As a quick guide, from the home page click on ‘The Maps’ to see species distributions, distribution changes between years, abundance, comparisons with another species, and to overlay landscape and habitat features - elevation is particularly revealing. Clicking on a tetrad gives a species list with level of breeding evidence.

The maps allow comparison with the bird life of our neighbours. Perhaps you can suggest reasons why Yellow Wagtail breed along the Downs but are absent from the Chilterns in east Oxfordshire and Buckinghamshire. Will Ring-necked Parakeets continue to remain east of the county boundary near Reading?

We hope you will enjoy exploring this treasure trove of information. Free access results from the generous support of OOS and the other county bird clubs. Once you have had an opportunity to explore the site, let us know your views on setting up a similar site covering only Oxfordshire. The distribution maps would be the same - though at larger scale. The abundance maps may tell us a little more about the local situation and the summary information would be specific to our county. Also let us know if you have suggestions for local surveys, possibly covering all five counties.