4.1 Introduction
In broad terms the BBRC assess the sightings of rare bird taxa (species or sub-species) in Britain. What is ‘Britain’ is defined in Section 1.0. What is ‘rare’ and what constitutes a ‘bird species’ also need to be defined.
The starting point for the definition of ‘rare’ is taken as having occurred less than 150 times in the last decade. However as single invasion year could exceed this total and yet the species remains rare otherwise, a species is also considered ‘rare’ is there have been less than 10 birds in at least 8 of the last 10 years. These criteria are further refined below in section 4.4. criteria should be seen as guidelines, as other considerations, such as how easy a species is to identify is also taken into account.
‘Species’ definitions follow those of the BOURC as published in their BOU British Checklist and Annual Reports.
A full list of the taxa (species and sub-species) considered by the committee is published on the BBRC website (see Resources section). In addition, any species or sub-species not currently on the BOU British List would be considered by BBRC.
4.2 Sub-species considered
Diagnosable rare sub-species are considered by BBRC. For a sub-species to be considered, field or in the hand identification of a vagrant individual has to be considered possible with a high degree of confidence and they should meet the same criteria (in terms of frequency of occurrence) as the full species.
In addition, sub-specific identification of rare species will be applied where possible.
4.3 Indeterminate Species or sub-species Pairs or Groups
In a few cases, the Committee considers and publishes specifically indeterminate records of pairs or groups of rare species or sub-species, which are considered particularly difficult to separate in certain circumstances under present knowledge (see Appendix XX). In light of changing taxonomy, the list of pairs and groups remains under annual review.
Note that where identification criteria for species pairs are clearly established, indeterminate records will not be published and will be considered unproven.
4.4 Criteria for Removal
Species or sub-species, are automatically considered for possible removal from the list of those assessed by the Committee if more than 150 individuals have occurred during the past decade, with at least ten in at least eight of those years. Other species of slightly less frequent or consistent occurrence, especially those that are easy to identify, may also be considered for removal if they have occurred more than 200 times in the last 50 years, with 100 records in the last decade and at least ten records in eight of those years.
The list will be considered annually, with decisions to remove of species and sub-species reached by vote at the AGM.
