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NUMBER 89 99
FIGURE 11.—Skulls of Anatidae (dorsal views). Left to right: Anas, species undescribed (MNZ S33298, ex. H.O.
Forbes collection), from "Chatham Islands"; Anas chlorotis (MNZ 14978); Tadorna variegata (MNZ 16473,
male); Tadorna, species undescribed (MNZ S32830, presumed male), from Maunganui, Chatham Island. (Scale
bar=30 mm.)
the Te Whanga Lagoon (Turbott, 1990). The extinct species,
known also from mainland New Zealand, differs in being
somewhat larger, with a stouter bill and relatively shorter
wings. Its bones have been found in greatest abundance at
Waitangi West, at Tioriori, and at Te One Beach, near Red
Bluff, in deposits ranging in age from ca. 7600 (cf. NZA 3238,
locality 4) to ca. 700 (NZA 2603, locality 11) years old, but
they also occur commonly in middens. The Chatham Island
Duck, whose bones have been found at a considerable number
of sites on Chatham Island, but not elsewhere, was robust,
weighing as much as 2.5 kg (more than twice the weight of a
Grey Duck), and yet with wings perhaps even a little smaller
than in that species (pers. obs.). The new merganser {Mergus,
species undescribed), whose bones have been found in abundance
only in Te Ana a Moe Cave, was a little smaller than the
recently extinct (ca. 1905), flightless Auckland Island Mergan­
ser {Mergus australis; see Kear and Scarlett, 1970) and had a
shorter bill and even more reduced wings (Millener, pers. obs.).
EXTINCTIONS
The indigenous bird faunas of remote oceanic islands, having
evolved in isolation from most or all vertebrate predators,
are extraordinarily vulnerable to the impact of humans (see
Milberg and Tyrberg, 1993; Steadman, 1995). The land birds
and waterfowl of the Chatham Islands were well adapted to
their island environment. Most became larger than their mainland
counterparts, many became completely or nearly flightless,
some probably laid smaller clutches, and none developed
or retained a fear of mammalian predators. First human settlement
was almost certainly accompanied by accidental or deliberate
forest clearing, and on such small islands there would