Introducing the Thames and Chilterns Birds Atlas

A new internet based bird atlas ( has been launched, covering the counties of Bedfordshire, Berkshire, Buckinghamshire, Hertfordshire and Oxfordshire. For the first time it is possible to view in one place the breeding and wintering distributions and abundance for all bird species at the tetrad scale for a large tract of southern England as well as the changes since the 1980s, and for Bedfordshire and Hertfordshire, since the late 1960s.

 The area covered comprises 9276 sq km of inland southern England. From north to south it encompasses part of the southern Cotswolds, the vales of White Horse and Aylesbury, the chalk hills of the Chilterns and Berkshire Downs and valleys of the Thames and some of its southern tributaries. It includes substantial urban areas, such as Reading, Oxford, Luton and Milton Keynes; the outer metropolitan suburbs and a variety of habitat types. It is an area which has seen substantial changes in the 20th Century, in both rural and urban areas and these changes continue.

All of the counties undertook a tetrad breeding bird distribution survey during the period 1980 to 1992 (but most in the mid- and late 1980s) and again during the period of the most recent national British Trust for Ornithology (BTO) Atlas (2007-2012). In addition, Bedfordshire and Hertfordshire undertook one at the time of the first BTO breeding atlas in the late 1960s and early 1970s, and four of the counties (Berkshire, Buckinghamshire, Hertfordshire and Oxfordshire) achieved almost 100% coverage of their tetrads for timed tetrad counts in both the breeding season and winter during the 2007 to 2012 BTO Atlas survey period. The results of all of these are presented on the website.Its aim is to provide a source of information for birdwatchers and naturalists interested in the wildlife of the area, a reference source for local policy makers assessing the species and sites whose conservation should be promoted and a source of information for scientists researching population changes and density and their relationship to habitats.

The site enables users to compare the distribution between species and between different surveys. Habitat information derived from derived from 1km habitat mapping carried out by the Centre for Ecology and Hydrology has been used to create habitat comparison maps and overlays of habitat types to use with species and species comparison maps. As such it provides a unique opportunity to see changes over a period of 20 years, or 40 years in the case of Bedfordshire and Hertfordshire, at a much finer scale than the national 10km atlas, and to compare these to habitat data.

Some well-known national trends, like the retreat of some declining farmland species, such as Grey Partridge and Corn Bunting, can be tracked, as can the spread of species such as Buzzard, Red Kite and some of the recent arrivals like Cetti's Warbler and Little Egret. There are though other changes that can be investigated, such as the decline of species once regarded as successful colonisers of urban areas, like House Sparrow and Starling, or the differing trends amongst waders, with some little-known changes such as Curlews starting to breed on the Berkshire Downs despite losses in the valleys of the Upper Thames tributaries. There are many other such stories too be investigated, and hopefully the information presented here will inspire some visitors to the site to use the data to investigate further some of the factors that may be influencing these changes.


The project has been funded by the Bedfordshire Bird Club, Berkshire Ornithological Club, Buckinghamshire Bird Club, Hertfordshire Natural History Society/Herts Bird Club, Oxfordshire Ornithological Society and  the Thames Valley Environmental Records Centre. They are grateful to all the field workers whose efforts produced these maps and their colleagues in the Banbury Ornithological Society and Newbury District Ornithological Club for their help in organising the surveys, to the BTO whose generous extension of the on-line facilities set up for the 2007-2012 national atlas was an enormous help in realising the most recent surveys and to Garganey Consulting for designing and setting up the site.

For more information, please contact:-

For Bedfordshire Bird Club -;

For Berkshire Ornithological Club;

For Buckinghamshire Bird Club -;

For Hertfordshire Natural History Society/Herts Bird Club -;

For Oxfordshire Ornithological Society -;

Posted: September 21, 2016