Systematic List

The British List consists of three categories where acceptable records are placed.

The categories are defined as follows:

A) Species that have been recorded in an apparently natural state at least once since 1 January 1950.

B) Species that were recorded in an apparently natural state at least once between 1 January 1800 and 31 December 1949, but have not been recorded subsequently.

C) Species that, although introduced, now derive from the resulting self-sustaining populations.

D) Species that would otherwise appear in Categories A-B except that there is reasonable doubt that they have ever occurred in a natural state. This includes species that certainly arrived with a combination of ship assistance and provision of food and shelter, tideline corpses and birds that would appear in Category C but whose population is not self-sustaining. They form no part of the British List, and are not included in the species totals.

E) Species classed as escapes from captivity.

NP) Species included here have been published in various journals, but have found to be not proven for the species to be admitted in Category A-C prior to 1950.

Where a locality is on the border of two counties, it becomes a dual-county record, but if a bird is found in one county then moves to another county it forms two records with only the first sighting counting in the totals.

Other dual-county records are due to counties working with the Watsonian county boundaries to keep consistent recording data with the neighbouring county adopting the 1974 goverment changes.

In 1985 'At sea' records were considered for the first time by the British Birds Rarities Committee (BBRC) and this area was referred to as the UK Economic Exclusion Zone. The boundaries are defined as 200 nautical miles (370 km), except where there is a median line between countries.