species they resembled more. Only the former had a distinct nuptial (breeding) plumage: the head was green as in mallard drakes, but less glossy, with some buff feathers on the sides, a dark brown eyestripe and a faint whitish ring at the base of the neck. The upper breast was dark ruddish chestnut brown with blackish-brown spots. The wing patch (speculum) and the tail was also like in mallard drakes' nuptial plumage, including curled-up central tail feathers, but the tips of the speculum feathers were buff. The underside was a mix between the vermiculated grey feathers of the mallard and the brown ones of the Pacific black duck. The remainder of the bird looked like a male Pacific black duck with lighter underwings. The bill was black at the base and olive at the tip, the feet reddish orange with darker webs and the iris brown. The eclipse plumage looked similar to a dark eclipse mallard drake. Males of the "superciliosa" type resembled a Pacific black duck with a less distinctly marked head, the supercilium and cheeks being buffy and the cheek (malar) stripe hardly visible. The upper breast, flank and scapular feathers had broader buff edges, and the underwings were lighter. The speculum was usually as in the "platyrhynchos" type, i.e. mallard-like, but at least two specimens have the green speculum of the Pacific black duck. The bill was like that of A. superciliosa, and the iris and legs similar to the "platyrhynchos" type. Females looked essentially like a dark mallard female with the orange of the feet and near the bill tip usually a bit more pure. Distribution It occurred, in recent times at least, on the islands of Guam, Saipan and Tinian. Two unidentified ducks were seen on Rota in 1945, but as no movement of A. oustaleti between Saipan and Tinian, which are just apart, was recorded, these were probably vagrant migrating ducks, although Marshall (1949) suspected from circumstantial evidence that such movement did indeed take place. However, the distance between Guam and Rota is nearly , making intentional migration between these islands unlikely. Ecology and behaviour The Mariana mallard inhabited wetlands, mostly inland but occasionally also in coastal areas. On Guam, it was most abundant in the Talofofo River valley, on Tinian on Lake Hagoi and Lake Makpo (before it was drained and known as Makpo Swamp), and on Saipan on the Garpan Lagoon and