Methods

The Suffolk working group from the outset decided to survey every tetrad, which included any land within the Suffolk boundaries, whereas, the national survey aimed to cover every 10-km square and to have timed counts in at least eight tetrads in each.

When comparing this Atlas with previous Atlases there was a very important difference in the way that data were collected. The BTO developed a dedicated online system to allow Roving Records and Timed Tetrad Visits to be submitted online; also fieldworkers could access web pages to see where gaps in fieldwork were required.

There were two types of fieldwork:

  1. Timed Tetrad Visits (TTVs): recording and counting all the birds seen or heard in a 2 x 2-km square during timed visits of one or two hours, in the winter and the breeding season.
  2. Roving Records: recording any bird, at any time and at any location.
TTVs required two one-hour count periods that were carried out twice over the winter period and again during the breeding season in every tetrad (2 km x 2 km square). These counts were designed to provide an estimate of relative abundance in the 10-km square.

The required periods for fieldwork were: For winter the early visit 1 November to 31 December and the late visit 1 January to 28/29 February and for summer fieldwork the early visit 1 April to 31 May and the late visit 1 June to 31 July.

What to count: Observers were asked to count only individuals that were using the square. They were to ignore individuals flying over the square except, for example, hunting raptors and hirundines that were effectively ‘using’ the square. During the breeding season juveniles were excluded from the counts. On the coast, birds were counted as far offshore as the observer was confident in identifying them, provided they were still in their tetrad. Anything offshore but not in the tetrad should be submitted as a Roving Record for the appropriate tetrad. All introduced and feral species were to be counted.

Colonial nesting species (inland or coastal): If a colony (one or more nests) was encountered these were to be recorded in the ‘Colony Table’ on the recording form. The minimum requirement was to tick that a colony was present on either of the visits and if possible to count the colony. The maximum count of Apparently Occupied Nests or the number of individuals in the colony was required. Shading on the Colony Table gave guidance on which method to use for specific species. Only rough estimates were required. Any colony nesting species encountered away from the colony were to be counted and recorded in the main part of the recording form.

Stopping the clock: if a flock of birds, a colony, or a particularly ‘busy’ area (e.g. a wood at dawn chorus) was encountered the clock could be ‘paused’ in order to do the counting. When counting large aggregations, or areas with high densities, an approximate count was only required.

Roving Records, the aim in Suffolk was to compile comprehensive species lists for every tetrad (2 km x 2 km square) in both seasons. These data will form the basis of all the distribution maps in the final production.

Breeding evidence: During the breeding season the fieldworkers were asked to record the highest evidence of breeding for each species in every tetrad. The aim was always to confirm breeding if possible. The various levels were recorded using standard codes.

The code F (flying over) was only to be used for roving records, as birds flying over were excluded from TTV counts.

Non-breeding birds

Possible breeding Probable breeding Confirmed breeding The final data collection included records extracted from Bird Track, The Breeding Bird Survey , Nest records, Ringing, and from Wetland Bird Survey counts.

Summer TTV Map Winter TTV Map

Summer TTV Pie chart Winter TTV Pie chart