Vagrants and the Paucity of Land Bird Species at the Prince Edward Islands

The present avifauna of the sub-Antarctic Prince Edward islands consists of twenty-nine breeding species, including only one land bird. Vagrant land birds recorded during 64 months at these islands include twenty-eight individuals (twelve species of Palaearctic migrants, eleven individuals (five species) of resident African birds and four unidentified passerines. Cattle Egrets Bubulcus ibis, European Swallows Hirundo rustica and waders (Charadrii) were most frequently reported. Few of these birds were seen for more than a few days at these islands and none was seen for longer than 2 months. Although the remoteness of the islands precludes immigration by the less mobile birds, the apparent paucity of land bird species is largely atrributed to the failure of immigrants to colonize. Most species which arrived could not be considered to be potential colonists. The islands have a low ecological diversity and there appear to be few, if any, food resources which could be exploited at present by immigrant land birds. Climatic factors, predation and the lack of suitable vegetation cover may also exclude potential colonists.