The committee has a chairman, a secretary, and ten voting members, and is supported by others who serve in an advisory capacity. Since its inception, a total of 69 people have served on the committee as assessors. In addition to assessing annual records of rare birds, the committee conducts regular reviews of batches of previously accepted records on a species-by-species basis, to ensure that only those consistent with advances in knowledge of bird identification are retained, and to determine the subspecies of accepted records. Several species have been problematic for assessment, and extreme examples have taken more than 20 years from initial observation to acceptance. The committee has been criticised for its approach to assessing records where only one observer was present, for not publishing reasons for rejecting the validity of records, and for placing undue weight on descriptive detail when assessing record submissions. Seabird identification has proved particularly difficult, leading some observers to suggest that the committee sets too high a standard.