HENDERSON PETREL

Named after the only island on which it is known to breed, the Henderson petrel is a medium-sized, slightly built gadfly petrel (Pterodroma species) with fairly uniform grey-brown plumage. The underparts are slightly paler, and the feathers of the forehead and chin have greyish tips, giving a more mottled appearance around the beak. The underside of the wing has a pale leading edge between the wrist and the body, and the bases of the primary feathers are silvery-white (2) (3). As in other gadfly petrels, the Henderson petrel’s beak is relatively short and stout, and is equipped with a powerful hook and sharp cutting edge, used for gripping and cutting up its prey (4). The beak is black, while the legs are pink and the feet have dark tips (2) (3). The most common call of the Henderson petrel is a repeated kyek-kyek-kyek-kyek, given both in flight and from the ground (3).

Until quite recently, the Henderson petrel was considered to be a dark form of the Herald petrel, Pterodroma heraldica, which is distinguished by its pale belly. In addition to this plumage difference, the two species were split based on the fact that they do not appear to interbreed, tend to breed on different parts of the island and in slightly different seasons, and have different calls. Studies have also shown genetic differences between the two (5).