Worcestershire Record No. 21 April 2007 pp. 20-21


Harry Green. BTO Regional Representative in Worcestershire.

The next important project from the BTO is to produce an even newer Atlas of the Birds of Britain and Ireland. This is a continuation of a series of projects and follows on the previous breeding bird atlases and the one on winter birds, but for the first time both breeding and winter fieldwork is happening during one time period of several years.

After field work and trials a clearer picture of the work involved has emerged. The following is derived from information circulated by BTO to Regional Representatives and should give readers an idea of what to prepare for! As organiser for Worcestershire I’m hoping for lots of keen volunteers! Having been involved in collecting records 1968-1973 (the first Atlas) and in organising the surveys in Worcestershire for the others, I do wonder whether I shall actually see the new one in print!

The survey is based on the 10 km squares of the National Grid and the tetrad (2x2 km) sub divisions. If anyone reading this would like to take on surveying a 10km square please get in touch with me. An ideal approach would be for one (perhaps two) people to co-ordinate and collate effort by a number of observers in one 10km square.

It is highly likely that the internet will become and important way of submitting records to BTO as can be done now by BirdTrack.

Aims of the Atlas

To produce dot distribution maps showing in which 10-km squares each species winters or breeds.
To produce maps showing broad patterns across Britain and Ireland of relative abundance during winter and the breeding season.
To measure changes in distribution and abundance patterns since earlier Atlases.

To fulfil these aims, Atlas fieldwork must provide:

A complete species list for each 10-km square in winter and breeding season.
A measure of (relative) abundance for each species in each 10-km square in winter and summer.


Winter = beginning of November to end of February; 4 winters, 2007/08 to 2010/11.
Breeding Season = beginning of April to end of July; 4 seasons, 2008 to 2011.

General principles for both seasons

Fieldwork will comprise a balance between ‘Roving Recorders’ and ‘Timed Tetrad Visits’ – the two together providing the total species list and evidence of breeding, whilst the latter will also provide the required abundance data.
  It is essential to stress the equal importance of both approaches.


Roving Recorders will have a very free remit – simply to provide records of species with the aim of amassing comprehensive species lists for 10-km squares. For example, these might arise through one-off ‘casual’ type records (e.g. a bird flying over the garden, something seen from motorway), a day’s birding through several 10-km squares, or dedicated searches of the habitat in a 10-km square for hitherto missed species.

Timed Tetrad Visits are more structured:

Each Timed Tetrad Visit will comprise a compulsory 1st hour, and an optional 2nd hour, during which individuals of each species seen and heard will be counted. There will also be space on the form to continue beyond 2 hours to search for species not already encountered, and to seek evidence of breeding.
In a season (winter or summer) there will be two such visits, one early and one late. For winter this means one visit in Nov-Dec and one in Jan-Feb. For the breeding season this means one in Apr-May and one in Jun-Jul. A tetrad need only be surveyed in one summer and one winter.
The aim will be for each 10-km square to receive Timed Tetrad Visits to at least 8 tetrads in summer and at least 8 in winter. Ideally, these would be the same 8 tetrads in summer and winter.
The choice of which 8+ tetrads to survey is up to the individual observer. However, to facilitate comparison with the last breeding Atlas, it would be beneficial if those tetrads visited last time (which was also the observer’s choice) were revisited. We will provide lists of these tetrads to local organisers. There is also some merit in squares containing a BBS square receiving an independent Timed Tetrad Visit to enable comparisons between BBS and Atlas counts.

Evidence of breeding

Among BTO Regional Representatives polled, there was widespread support for adopting the 3-level system for evidence of breeding. Thus we will follow the European Bird Census Council and most local atlases in requesting the evidence of breeding (e.g. singing; bird with food; nest with eggs). This information will be sought from Timed Tetrad Visits and Roving Records. Further information will be given on how to record such information without detracting from other activities. Evidence of breeding is also being built into BirdTrack as an optional field to facilitate further data capture.

Watch this space!

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