In the presentation of his list of Recent Holarctic Bird Species, Voous (1973) was convinced, after consultation with many ornithologists from all parts of the world, that the time had not arrived for an attempt to reach reasonable agreement on a list of bird species of the world. Today, more than 25 years and several world lists later, and while the enormous undertaking the Handbook of the Birds of the World (Del Hoyo et al. [in series]) is well under way, consensus has still not been reached. While Voous' lists (1973, 1977ab) have been the standard for many years, several amendments have been published by the BOU Records Committee (BOURC) and more recently by the Dutch committee for avian systematics (CSNA). For Atlantic Seabirds, a joint venture between a UK and a Dutch organisation, this means that different lists and sequences, even different systematic principles, have been adopted in either country. The debate will go on, no doubt. Meanwhile, there is scope for confusion and there is an increasing risk for misunderstanding. For example, most ornithologists refer to the Lesser Black-backed Gulls Larus fuscus as a polytypic species that includes a very black, small and slender nominate race in the north and east of Europe, and two paler, bulkier races around the North Sea (L.f graellsii and L.f. intermedius). The CSNA considers the Baltic Gull L. fuscus and Lesser Black-backed Gull L. graellsii as specifically distinct, and ‘intermedius’ is considered conspecific with graellsii (Sangster et al. 1999). Similar decisions were published for the soft-plumaged petrel complex Pterodroma mollis/ maderia feae, for Cory’s Shearwaters Calonectris diomedea/ borealis/ edwardsii, Manx Shearwaters Puffinus puffinus /yelkouan /mauretanicus. the herring gulls/yellow-legged gull complex cachinnans/ michahellis. Larus argentatus/ Previously, the BOURC has suggested changes to the British and Irish List (e.g. BOURC 1991, 1998). For example, Sula bassana was changed to Morus bassanus, a proposal adopted by CSNA only in 1997. The mediterranean subspecies of Manx Shearwater was accorded species status Puffinus yelkouan (including subspecies mauretanicus), while the nominate was now considered monotypic. However, CSNA has split this complex (for Europe) into three distinct taxa (Table 1; Sangster et al. 1999).