Coexistence of two species of Halipeurus (Phthiraptera) on Chatham Island taiko {Pterodroma magentae) (Aves)

Feather lice (Phthiraptera) were collected from 14 Chatham Island taiko (Pterodroma magentae). These included two species of Halipeurus (Philopteridae) in the ratio of two H. procellariae to one H. theresae. So far as we know, the regular occurrence of two Halipeurus species on a host is unique. H. procellariae is likely to have been acquired from the taiko's ancestors, but H. theresae probably derives from a secondary infestation through close association of the host with Chatham petrels (Pterodroma axillaris), probably in mixed breeding colonies. From sub-fossil evidence, Chatham petrels formerly bred on the main Chatham Island, to which P. magentae has, from such evidence, always been restricted.