Mangaia crake

Mangaia crake Temporal range: Late Holocene
Conservation status
Extinct (15th century)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Gruiformes
Family:	Rallidae
Genus:	Porzana
Species:	†P. rua
Binomial name
†Porzana rua Steadman, 1986

The Mangaia crake ("Porzana" rua) is an extinct species of flightless bird in the rail family, Rallidae. It was described in 1986 from subfossil bones of late Holocene age found in caves on the island of Mangaia, in the southern Cook Islands of East Polynesia. It was placed in the then-loosely circumscribed genus Porzana, but it almost certainly does not belong to Porzana proper as understood in modern times. Rather, it most likely was one of the crakes which are now separated as genus Zapornia. While the species survived for hundreds of years of Polynesian settlement, even despite the establishment of introduced predators, at some point in the last millennium Mangaia suffered an ecosystem collapse with far-reaching consequences, the extinction of "P." rua among them.

The species name rua is Marquesan for a hole in the ground, be it a sinkhole, a grave, a chasm or a cavern. It alludes to the name of the type locality, Te Rua Rere ("The Flying/Jumping Cave"), als well to the fact that the prehistoric deposits of Mangaia were metaphorical "graveyards" of extinct fauna, with this rail being one of the most numerous.

Description

It was a good-sized crake, about as large as the similarly flightless and possibly very closely related Henderson crake (Zapornia atra), or a small plump sora (one of the species remaining in Porzana today). Probably weighing 65-70 g, it was less than 20 cm long altogether, including a short tail of about 35 mm and a bill perhaps 20-25 mm long. By Zapornia crake standards, the midfoot bone (the "lower leg" of birds) was long, the femur fairly short but notably stout for a bird of its size and bulk. Humerus and ulna were shortened (and the ulna was also more delicate), even a bit shorter than in the smaller but volant Spotless crake; assuming its remiges were short as in the Henderson crake, the wing length of "P." rua was probably about 6 cm or even less.

Its plumage colour is unknown. Assuming it does indeed belong to a group including some or all of as Henderson's crake, the Spotless crake, the Kosrae crake and the Tahiti crake, it was almost certainly mostly blackish, with perhaps some barring on the hindflanks, and/or a slightly paler underside and a darker and olive-tinged back and wings. Its bill would in this case most likely have been red or blackish, the eyes chestnut brown, and the legs almost certainly bright red.

History

The cause of its extinction is ascribed to a combination of predation and habitat alteration following human settlement of the island and the introduction of exotic mammals.

See also

• List of birds of the Cook Islands